Windows won't initialize because of *.dll errors

I received the following error message as my Windows XP machine boots up: This application has failed to start because OLEAUT32.dll was not found. Re-Installing the application may fix this problem" In the blue bar across the top of the error box, it adds the following: “Isass.exe - Unable to Locate Component.”

I was able to click through this error message but received a series of identical error messages, each time with the blue bar at top citing a different component - userinit.exe, services.exe, explorer.exe. Eventually I reached the Windows background screen, but my desktop did not initialize.

From this point I tried to run Task Manager, but got a message that OLEPRO32.dll was missing. I was able to click through that error message and get to Task Manager, and ran the command prompt. I determined that both file OLEAUT32.dll and OLEPRO32.dll were not present in the ..\Windows\System32 directory.

I made a copy of both missing *.dll files from another Windows XP computer and installed them on the problem system using DOS copy from the command prompt and rebooted. Everything seemd peachy keen, no error messages and Windows desktop initialized just fine. However, the next time I rebooted the system, I was back where I started from - with the error message that Oleaut32.dll was missing.

It sounds like my machine has become infected with a virus or a trojan horse to me, but I can't seem to locate any useful information at any of my usual sources on the internet. Has anyone seen this problem before or have any idea what’s going on.

I should add that this problem seems to have occurred shortly after running some anti-spyware software (AdAware 2008 and Spybot Search & Destroy) and the registry and optimization tool CCleaner on the problem system. I’m not sure if any of these are the actual cause, since the problems did not occur immediately after performing these maintenance tasks; however, they are the only system level activity I performed on my computer during this timeframe, which is why I am suspicious of them.

Help is appreciated.