My thinking is that the boot sector is probably infected. If I were you, I would try and copy any important data files to some other location for safekeeping and then reinstall the OS and wipe it completely. Trying to eradicate all the viruses on a very badly infected windows machine can be a huge waste of time and you honestly won't really know if it's really clean. Reinstalling the whole OS might take you some time, but you can be sure it won't have viruses. The only real consideration in my opinion is whether the windows install has some special software installed which you might lose by doing this.

thanks a lot ,i have finally scanned my partition ,its working fine now.

Viruses affect among other things , executable files, dlls , boot sectors. Viruses are not separate files by themselves. So you can not just identify and delete them. More often they will copy themselves into the executable image.
In that case you have to back up your files from a clean source

thanks a lot all of you for the help.i had a power failure in this part of the world.
so really sorry if some one thought that i was so very mean
.

thanks again till the next problem...