"Windows cannot modify the drive letter of your system volume or boot volume."

I checked the "My Computer" window, and F: drive was assigned to my primary hard drive. C: and E: drives had been assigned to my the 2 slots in my 7-in-1 card reader as "Removable Disk(s)", and my CD drive was designated as D: drive.

 

So how do I change the drive letter names within Windows XP so that C: represents my primary hard drive? I can manually change the current drive letters set for the 7-in-1 card reader using the XP Disk Management snap-in, but when I try to change my hard drve's letter, I receive an error message that says "Windows cannot modify the drive letter of your system volume or boot volume." 

 

Solution:

1. Start regedit

2. Go to the following registry key: HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices

3. Find the drive letter you want to change to (new). Look for "\DosDevices\C:".

4. Right-click \DosDevices\C:, and then click Rename.

5. Rename it to an unused drive letter "\DosDevices\Z:". This frees up drive letter C.

6. Find the drive letter you want changed. Look for "\DosDevices\F:".

7. Right-click \DosDevices\F:, and then click Rename.

8. Rename it to the appropriate (new) drive letter "\DosDevices\C:".

9. Click the value for \DosDevices\Z:, click Rename, and then name it back to "\DosDevices\F:".

10. Restart the computer.

 

Here is a link to a Microsoft Knowledge Base article that provides the instructions.
http://support.microsoft.com/default.aspx?scid=kb;en-us;223188