By Serdar Yegulalp
Technical Editor

WINDOWS 95 MAY BE robust, but it also has a sensitive side-particularly when it comes to your hard disk. If you're running Win95 and you're about to add or remove IDE or SCSI hard disks, or change the partitioning of existing ones, be gentle and work carefully. Here's some advice to get you started. Take heed of the drive lettering scheme. Windows 95 automatically assigns drive letters to most storage devices.

If you install software with files on a certain drive, and the addition of a new hard disk shifts the drive lettering, that program will probably complain about missing files when you try to run it. Some programs reside entirely on one drive and aren't sensitive to these kinds of changes, but others are, so pay close attention.

• First floppy drive (A: )
• Second floppy drive, if any (B: )
• IDE chain 0, device 0 (master) (C: )
• IDE chain 0, device 1 (slave)
• IDE chain 1, device 0 (master)
• IDE chain 1, device 1 (slave)
• Non-boot SCSI devices

Win95 always gives the two floppy drives and the first hard drive letters A, B and C, respectively. It assigns each remaining device a letter depending on the order in which it's detected. For example, if your CD-ROM drive is on IDE chain 1, device 0, it would be designated with the letter D. (If possible, you should put your CD-ROM drive on a seperate chain.) Floppy and IDE hard disks take precedence over everything else.

A second IDE hard drive, for example, may displace an existing CD-ROM drive letter assignment. If your older CD-ROM-based programs look for the CD-ROM as drive D: , but it's been renamed F: , you may have to reinstall the programs or at least fix the broken drive reference. A shortcut that points to a drive that no longer exists will alert you to this when you activate it. However, if the shortcut points to a drive that now has different contents, it will still attempt to search for its original target on that drive.

Another potential problem results if more than four other hard disk letters exist, which can happen if you've partitioned a disk into one or more logical drives. When you set up a hard disk, you're given the option of allocating all the space on the disk or segmenting it into two or more virtual, or logical, drives. This process, known as partitioning, is done with a DOS program called Fdisk. Fdisk is run from the command prompt, but it should ideally be run only when Windows 95 has been booted in command-line mode. Don't run Fdisk from the Start button's Run option, as this can cause problems.

Before you partition a disk, the best thing to do is assign the CD-ROM drive a fairly high letter. Try R: for CD-ROM. Next, determine which programs depended on the old CD-ROM drive letter. You'll need to reconfigure or reinstall these programs, but it's a lot less trouble than messing with partitions. It's difficult to change assigned partitions without destroying everything on the disk.

To change drive letter assignments for a CD-ROM drive or other non-BIOS device-such as a removable drive recognized only by a Windows 95 driver-open Device Manager, either by right-clicking on My Computer and selecting Properties or by double-clicking on System in Control Panel. Open the sub-branch of the tree that should contain your device-such as CD-ROMs-and double-click on the device. If you don't see your device in the tree, a DOS device driver is controlling it, and you probably need to change it by editing settings in either CONFIG.SYS or AUTOEXEC.BAT. Look for the MSCDEX.EXE statement in AUTOEXEC.BAT, which is the most common way a drive letter is assigned to a CD-ROM via a DOS device driver.

Next, choose Settings. At the bottom of the dialog you'll see a field for the Current Drive Letter Assignment and two fields under Reserved Drive Letter-one for Start, the other for End. Set the Start and End drive letters to the range of letters that can potentially be assigned to the device (start from nearer the beginning of the alphabet, of course). If you set the drive range for the CD-ROM from D: through F: , for instance, and you don't have a hard drive assigned as D: , the CD-ROM will be set to D: . Later, if you add another hard drive as D: , the CD-ROM will be reassigned as E: . When you're finished, click on OK, shut down and reboot to implement the changes.

If you install new partitions or remove old ones, reboot Windows 95 completely, in normal mode, each time. Every full reboot re-registers the changes in drive lettering and lets you see the full impact of what you're doing.

Drive changes can damage your system configuration, but Hardware Profiles are an easy way to protect your setup. The Hardware Profile feature is a little-used but powerful way of storing different hardware configurations (see the Power Windows column in the June issue). Changes in drive configurations are a perfect use for these profiles. This way, if you make a mistake and want to start over, you can at least reset your software settings with ease. Here's how to do it.

Right-click on My Computer and select Properties. Choose the Hardware Profiles tab. Unless you're using a laptop, you should see only one profile-Original Configuration. Click on Copy to make a duplicate of this configuration and type an appropriate name for your new configuration-perhaps New Drives. Select OK. Shut down your computer and make the necessary hardware changes. When you start to reboot, Windows 95 will ask which Hardware Profile you're running. Choose the newly created profile and continue booting.

If you want to undo the changes you've made, you can easily go back to your original system settings by selecting Original Configuration at boot-up.

Some of the more common calamities associated with changing or installing drives aren't necessarily fatal, but they can be annoying and disruptive. Here are three of the most common problems and what to do about them:

Your system no longer boots. This may happen if you're trying to attach a new drive to the same IDE chain as the boot drive. Check the master/slave settings on the drives; the boot drive should always be set to master mode. Make sure the BIOS settings for the drives are still correct. Also make sure all drives have power and that their signal cables are correctly installed at both ends.

Not even Fdisk recognizes your installed drives. Incorrectly configured hardware is usually the culprit here. Make sure your BIOS has recognized and installed the drive before you attempt to run Fdisk. Not all computers automatically register a new drive-some require a manual BIOS change before they recognize anything new. This is especially deceptive with systems that at boot time display the devices attached to each IDE controller. Just because you see it there doesn't necessarily mean the system will use it.

Windows 95 shows more drives than should be present. This can happen if you change drive configurations or partition more than once.

If you check the Performance tab in My Computer's Properties option, you may see several "ghost drives" that weren't there before, all of them in MS-DOS compatibility mode. Also known as safe mode, MS-DOS compatibility mode is a means of booting Win95 without 32-bit components.

One safe and simple way to correct the "ghost drives" problem is to disable any changes, create a new Hardware Profile, shut down, restore the changes and reboot under the new profile.

A permanent solution is one that will affect this and all future Hardware Profiles. It's a little risky, so don't attempt it unless you're an experienced user. You need to do some spelunking in the Registry to remove outdated drive entries. Using REGEDIT, go to HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Class\hdc and delete all the keys beneath it. Don't delete the hdc key itself, though. Win95 needs it there even if it's empty (it almost never is). One important caution: Be sure to back up your Registry before you attempt this!

Many drive upgrades involve changing a disk controller card. You need to do this if you intend to use your new drive as a boot disk, for example, and your computer's controller BIOS doesn't support Enhanced IDE drives bigger than 528MB. (You'll need to upgrade any IDE BIOS dated earlier than January 1994.)

If you're upgrading your motherboard's drive controller with a newer one on a plug-in card, make sure the computer has options in its ROM BIOS to let you disable the built-in controller. A lot of pre-1990 motherboards don't have this option, so upgrading your motherboard may be the only solution.

Windows 95 automatically works with most plug-in IDE controller cards when you boot, so there may not be a need to redetect hardware. But if the motherboard doesn't allow you to disable the built-in controller, the plug-in controller will show up in the Device Manager, but it won't be usable. It will appear either with a question mark above it, indicating it has an initialization problem, or with a red X through it, meaning it's disabled. Once again, the only solution is a new motherboard.

Finally, if you want to be extra safe, use Windows 95's Hardware Profiles to make a separate profile for the new setup.