Is keeping the primary hard disk as disk C: still relevant?

Your computer can use up to 26 drive letters, from A through Z. Use drive letters C through Z for hard disk drives. Drive letters A and B are reserved for floppy disk drives. However, if your computer does not have a floppy disk drive, you can assign these letters to removable drives.

From the allknowing Microsoft Knowledge Base

Before you modify drive-letter assignments, note the following items:

• Changing the drive letter of the system volume or the boot volume is not a built-in feature of the Disk Management snap-in.
• Many MS-DOS-based and Microsoft Windows-based programs refer to specific drive letters for environmental or other variables. If you modify the drive letter, these programs may not function correctly.

How to remove a drive letter

To remove an existing drive letter on a drive, on a partition, or on a volume, follow these steps:

• Log on as Administrator or as a member of the Administrators group.
• Click Start, click Control Panel, and then click Performance and Maintenance.
• Click Administrative Tools, double-click Computer Management, and then click Disk Management in the left pane.
• Right-click the drive, the partition, the logical drive, or the volume that you want to assign a drive letter to, and then click Change Drive Letter and Paths.
• Click Remove.
• Click Yes when you are prompted to confirm the removal.
• The drive letter is removed from the drive, from the partition, or from the volume that you specified.

Yes, you should keep your primary hard disk as C:, because there's still a lot of software that has paths hard-coded into it in one way or another. Alternate drive letters for the primary hard disk is something that almost no one tests for, and so you'll end up finding subtle breakage in lots of places.

I'm not saying that you shouldn't be able to do it (heck, Windows works just fine if you install to a primary other than C:), but you don't have a Windows computer just to run Windows, you'll want to put on other software. And there's plenty of companies out there that can't get it through their heads that they need to use the variables, not hard code paths.

So, if you want a 'it just works' experience, keep your primary hard disk as C:, and have Windows installed in the default location.

You can survive doing it otherwise, but you'll regularly run into annoying problems.

You would be amazed at how many freshly developed, "cutting edge" applications assume c:\ to be the primary hard disk.

The convention may be outdated but guys who write the apps are still pretty "dated" for lack of a better word :)

My recommendation? Keep the C:\