Help! Windows XP Logon problem

My computer is a P1.8 notebook with Windows XP SP2. Yesterday when I turned it on it start to go into chkdsk and ran a lot of disk consistency scans, saying that some sectors were changed. After it had fixed it an got onto the Windows Login screen, I got a prompt saying that "Winlogon.exe failed to load due to missing file sfc_os.dll, reinstalling this application may fix your problem". Once I clicked OK and got into Windows, computer was running very slow and the contents in my Desktop and My Documents were missing! What is going on here? Was my harddisk damaged and data is now gone missing?

Any advices would be greatly appreciated!

 

Sounds like your infected.Read and follow the instructions fully
http://forums.majorgeeks.com/showthread.php?t=35407