Windows VISTA only starts in safe mode?

okay so a few days ago i downloaded an anti virus system (avast). it said thtat a windows32 file was a trojan horse. and so we delted it.....

Now it restarts every time we try to start our computer normally.. (its like it is on a time line thing because even if we don't log in it will restart after about a minute.) if we actually type our pass word it will load some things then just restart.. giving us options to start in

Safe Mode

Safe Mode with cmd

Safe Mode with networking (what im using now.)

if we try to use they system restore an error (unidentified error 0x80070057) shows up and so that dosnt work.

we tried restore using command prompt, bios and from the start menue... NOTHING has worked

any suggestions??

P.S. we don't have the restore disk.