Reset the default security provider in Windows XP
To reset the default security provider in Windows XP, delete the relevant registry keys in the Windows registry. To do this, follow these steps:

  1. Start the computer. Press the F8 key during startup to start the computer in Safe mode.
  2. Start Registry Editor (Regedt32.exe).
  3. Delete the following registry keys in the Windows registry:
     HKEY_USERS\.DEFAULT\Software\Microsoft\Cryptography\Providers
     HKEY_USERS\S-1-5-20\Software\Microsoft\Cryptography\Providers
  4. Quit Registry Editor.
  5. Restart the computer.

Reset the drive letter of the system drive
Use Registry Editor to change the drive letter of the system drive back to its original value. Edit the following registry key to change the value of the system drive:
HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices

For additional information and steps detailing the exact procedure to rename the system drive letter, click the following article number to view the article in the Microsoft Knowledge Base:
223188  (http://support.microsoft.com/kb/223188/ ) How To Restore the System/Boot Drive Letter in Windows

bbarsh wrote:Yes, I tried that already, but I can't find

HKEY_USERS\.DEFAULT\Software\Microsoft\Cryptography\Providers
    HKEY_USERS\S-1-5-20\Software\Microsoft\Cryptography\Providers

anywhere.

This sucks.

WORKAROUND
Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall your operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.

To work around this problem, use one of the following methods based on the error code that you receive.
Workaround for error code 0x80004005
To work around this problem, use one of the following methods.
Method 1
Note You should follow this method if this error code occurs after you upgrade from Microsoft Windows 98 Second Edition.

Start from the Windows XP CD-ROM, and then perform an in-place upgrade repair. Make sure that you use a valid product key. For more information about performing an in-place upgrade, click the following article number to view the article in the Microsoft Knowledge Base:
315341 How to perform an in-place upgrade (reinstallation) of Windows XP
You can also resolve this problem by uninstalling Windows XP. Then, reinstall the operating system that you were running before you upgraded to Windows XP. For more information about how to uninstall Windows XP, click the following article number to view the article in the Microsoft Knowledge Base:
312569 How to manually start the uninstall process to remove Windows XP




METHOD 2
To resolve the problem, repair the installation of Windows XP by using the Windows XP CD, and then replace the files. To do this, follow these steps:
1.         Insert the Windows XP CD in the CD drive or in the DVD drive.
2.         Restart your computer.
3.         When you receive the following message, press a key to start your computer from the Windows XP CD:
Press any key to start from CD
Note Your computer must be configured to start from the CD drive or from the DVD drive. For more information about how to configure your computer to start from the CD drive or from the DVD drive, see the documentation that came with your personal computer. Alternatively, contact the manufacturer.
4.         When you receive the following message, press R to start the Recovery Console. This part of the Setup program prepares Windows XP to run on your computer.

To set up Windows XP now, press ENTER.

To repair a Windows XP installation by using Recovery Console, press R.

To exit Setup without installing Windows XP, press F3.


5.         Press 1 to access your primary drive installation by using the Recovery Console.
6.         When you are prompted, type the administrator password. If you do not have an administrator password, press ENTER.
7.         Type cd %SystemRoot%\System32 , and then press ENTER.
8.         Rename the following files by using the REN command. To do this, type REN File_Name.extension File_Name.old at the command prompt.
•         Wpa.dbl
•         Pidgen.dll
•         Actshell.html
•         Licdll.dll
•         Regwizc.dll
•         Licwmi.dll
•         Wpabaln.exe
Note In the previous command, File_Name.extension represents the new file name. Additionally, File_Name.old represents the old file name.
9.         Type the drive letter of the CD drive together with a colon, and then press ENTER. For example, you type D: , and then press ENTER.
10.         Type cd i386 , and then press ENTER.
11.         Type the following commands individually. Press ENTER after each command.
•         Expand licwmi.dl_%Systemroot%\System32
•         Expand regwizc.dl_%Systemroot%\System32
•         Expand licdll.dl_%Systemroot%\System32
•         Expand wpabaln.ex_%Systemroot%\System32
•         Expand wpa.db_%Systemroot%\System32
•         Expand actshell.ht_%Systemroot%\System32
•         Copy pidgen.dll%Systemroot%\System32
12.         Type Exit , and then press ENTER to restart the computer.