you can try using crap cleaner, i have used that before. it worked well for me, if not, use your computers security system like "norton" to run scans.
hope that helped.

If you want to completely format your HDD(s) you're going to have to boot via the Windows installation disc and format them there. Then you can start again, by reinstalling the OS.

There is no other way that I know of to format the boot drive without the Windows installation disc. You can maybe get a program that does it but I'm not sure if such programs exist.

If you just wanted to get rid of viruses ect, you could boot into safe mode and run Malwarebytes and Hitman Pro to get rid of any viruses. To run these programs in safe mode you're going to have to have them on a USB flash drive.

If you are wanting to start again just reinstall a fresh copy of your OS. Once a virus has taken control of your comp then there ain't much choice.
If you have Malware you can find little programmes like IObit Malware Fighter.

Thanks for the help, I appreciate it +Rep all of you

So far as I know re-installing the operating system is the best way to start over but I'd recommend malwarebytes as anti-virus it is the best! and use ccleaner to get rid of all the temp files that eat up space on your comp