Not so technical? No issues.
Well, WFP is an added advancement for the systems Windows 2000 and higher.
WFP stands for Windows File Protection. There are set of files (EXE, DLL, SYS, Font files and others) that are protected by system. Protection does not include denying deletion only, but renaming, moving, replacing with another file (may be same but with different version file) or editing the file using any editor. Whenm any attempt is made by user (or known/unknown program) it is replaced to original file!
Test this by:
* Go to your System32 folder (C:\Windows\System32, for example). You may also type %systemroot%\System32 in Run dialog to go there directly.
* Locate Notepad.EXE, you may need to click on 'show system files' in Explorer.
* Delete Notepad.exe file. Do Refresh -- your file is back!! You also see it exists in Recycle Bin (if you didnt Shift+Deleted).
See in my article over there, there are links at buttom for more information. Click on 'LPSF.zip' file, download, unzip and run it. It requires W2K, W2K3, WinME or WinXP to run. No, It is not Virus of any Kind.