The subject behavior occurs because the Msvcp50.dll file is deleted during the upgrade, or replaced by Msvcp60.dll.
To fix this problem, either upgrade to SP2 (Service Pack 2), or extract a copy of Msvcp50.dll from the Windows XP CD-ROM:
1. Hold down the SHIFT key as you insert the Windows XP disk in the computer's CD or DVD drive, to prevent the Windows XP installation from starting automatically.
2. Open a CMD.exe window.
3. Type the following command and press Enter:
Expand <CD-ROM:>\i386\msvcp50.dl_ %systemroot%\system32\msvcp50.dll
Where <CD-ROM:> is the drive that contains the Windows XP CD-ROM.
4. Type Exit and press Enter.
5. Remove the Windows XP CD-ROM from the CD or DVD drive.
6. Shutdown and restart your Windows XP computer.