The problem is that I decided to change the bootable drive letter C to different letter. I could not do it through Control Panel, so I used Registry Editor to do it. Since I did not get any warning message, I mistakenly thought, that it will work... You know the result... I cannot start windows any more!...

Now, I have the second hard drive with the operating system on it (also XP) so I can access the other one. Will it be helpfull? And also, may be there is the way to boot from some kind of bootable disk to access the registry and change the letter?

Please help!!!

Hi & welcome!

What is the exact course of events when you boot? Do you get a specific messge? If so, what is it?

If you can boot to safe mode then you will be able to re-assign the drive letter thru > right click on "My Computer" > select Manage > Disk Management > right click on the drive you want to assign a drive letter to.

When I turn pc on, it gets to the Windows XP screen with the blue bar running from left to right, and then instead of Welcome screen, apears blue screen with Microsoft Windows XP logo on it and it stays forever. No error messages at all. It just cannot find operating system files, since it's probably looking for "C" drive and it does not exist any more... Disc management as far as I know (unless in safe mode it acts different) does not allow to change the "drive letter of the system volume or boot volume".

Grab a bootdisk from www.bootdisk.com first and get to the dos prompt.

Get to the C:\ prompt. Then type attrib -s -h -r msdos.sys and hit Enter to remove the system, hidden, and read-only attributes for this file.

Now type edit msdos.sys and hit Enter. In the resulting window, look for the section titled [Paths] and see if it has the lines WinDir=C:\Windows and WinBootDir=C:\Windows and make sure that the path after the '=' sign corresponds with wherever Windows is installed. (you will have to remember what you renamed the drive letter to)

If those lines are not present add them manually as follows:

[Paths]
WinDir=C:\Windows
WinBootDir=C:\Windows


After making the necessary corrections, save the file and exit the editor. Now reset the correct attributes for the file by typing attrib +s +h +r msdos.sys and hit Enter. Now reboot and see if it now boots correctly into Windows.

If this works and you can boot into windows - Immediately go into Disk Manager and correct the boot drive letter!

Thanks Hengis for advice! You suggest to get a bootdisc from www.bootdisk.com. I downloaded (may be mistakenly) "XP Quick Boot Diskette Files", unzipped the files, then copied them to the floppy disc. It did not work: the system won't boot from this floppy. Probably that's not the right files I got. What I did, I created a MS-DOS startup disc from "format 3 1/2 floppy" window. This one worked and I got to A:\> prompt. The only thing is that I am not very familiar with dos commands... I never used them before... I have no idea how now to get to C:\ prompt. I typed C:\ after A:\> and pressed enter. It said "invalid disc specification" or something like that. Then I tried J:\, since I renamed the C drive to J. Still the same message (invalid disc specification). Could you tell exactly how to get to C:\ (or J:\, whatever) prompt...
Sorry for my ignorance in this matter... And thank you again!

If you used an MS-DOS boot disk i.e anything before Windows 2000 then you probably won't be able to view any of the Hard drives because you drive will most likely be formatted in NTFS and MS-DOS/Win95/98 can only see FAT32.

Try download the Windows XP boot disk from this site.
http://support.microsoft.com/?kbid=310994
Download the correct disk for your version of Windows e.g Windows XP Professional or Home Edition.

You are correct with the DOS commands.
If the microsoft site doesn't help then you can try this one. It has two downloads, one that you can use on a floppy disk and the other is an image that you can burn onto CD.
http://www.ntfs.com/boot-disk.htm