Hello 
Since 5 days when Avast scan my computer, it finds a virus called WIN32 REVOP. I delete it, but it comes back everyday …
Any help will be greatly appreciated
I will take a SWAG (Sientific Wild Assed Guess), you are either using WinME or WinXP?
If so, this is the beauty and pain of system restore. When you make changes/delete something that windows thinks important it keeps a copy in the C:\System Volume Information folder in one of the _restore files (system, hidden, protected).
This is probably the location of the infected file and in order to get rid of it you will have to disable system restore, reboot, run avast again to confirm clean (it should be, when you disable system restore it deletes restore points and files). Once everything is clear you can enable system restore again, see windows help and support (winxp) ‘system restore’ for mor info.
HTH David
Thanks for your answer. Indeed I use Windows XP. I will try this and keep you informed about my success (?).