possible registry problem?

I was in a limited user account and switched user to enter an administrator account (XP Pro). After logging in I got a system registry query from SpyBot Search & Destroy that sounded like it was asking me to change from "Old Administrator" to "New (user name)" so I told it to deny the change. When I logged out of the account, it was no longer showing on my welcome screen. I thought a cold boot would solve the problem, but I'm not even getting the welcome screen. I'm getting a blinking underscore on a blank black screen. Any suggestions about how I fix this problem?

 

Try this first;

http://www.pcworld.com/howto/article/0,aid,112479,00.asp

 

Dan's link above mentions a boot floppy... I've had one of these at the ready for a long time VERY handy. Simply copy the 3 needed boot files from a standard Windows XP installation to the floppy disk. The files are different for XP Home, XP Pro, and XP MCE, so keep that in mind. Copy the boot.ini and ntldr and ntdetect.com to a floppy disk (or a CD will work too I suppose). Many times when XP won't boot, you can set the boot order to go to the device where this 'boot' disk is and the PC will boot to the desktop. However, I don't think you have a boot problem, I think your user profiles have been hosed. Using the "Last Known Good..." boot option or Safe Mode might work. If they do, you can try a system restore from there....
Good Luck!

 

"Using the "Last Known Good..." boot option or Safe Mode might work. If they do, you can try a system restore from there...."

But the machine needs to boot to get there......

These three files are "basically" (see note below) not different for different "flavours" of XP. These are "generic" files for detecting the O/S.

ntdetect.com;
http://en.wikipedia.org/wiki/Ntdetect.com

ntldr;
http://en.wikipedia.org/wiki/NTLDR

NOTE:
Other than boot.ini of course. This file outlines the hard disk and partition on which the O/S (XP or ??) is installed. This can vary on different machines, however the majority of machines use the first disk and first partition for the O/S install.

Hence the CAVEAT:
If you don't have an emergency boot floppy, you may be able to use one created on another PC running Windows XP or Windows 2000, but there's no guarantee that it will boot your machine.

 

Thank you both very much. Would you believe a simple Cntrl+Alt+Delete got me back into Windows? Even though I haven't managed to figure out yet how to get that administrator account pinned back to the welcome screen, I do know how to enter it and can work around that problem if I have to.

 

This is recommended for XP Professional only, as the Administrator account does not show (by installation default) in XP Home.

To display/re-enable the (master) Administrator account on the Windows XP PRO Welcome logon screen, start Regedit (or Regedt32) and go to:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\SpecialAccounts\UserList

If the "Administrator" DWORD key is present (in the right hand pane), Modify the Value to 1. (Highlight it, select Modify, check the Decimal box, type 1.) Click OK.
Close the Registry Editor when done. Restart.

If the "Administrator" DWORD key is NOT present, create a new Value:
right-click on an empty spot in the right hand pane, select New - DWORD (REG_DWORD), name it Administrator.
Click OK. Double-click on it, check the Decimal box type 1, click OK.

Now you should see the Administrator account on the Welcome display.