svchost.exe is infected by melware-trojan

[seekhelp]

My svchost.exe is infected with melware-trojan. To remove that I installed windows twice with format 1time. As still having the problem then tried regcure,Tuneup utilities, Trojan remover, Process explorer, McAfee and other source(use DOS to delete the file) to get rid of it.But everytime I open a folder the cirus guard says the trojan found and then if I say delete that the box closes but pops up again when opening another folder. And also cant open c: and d: drive. It always shows a open with box so then I need to select "Internet Explorer" to access the drive. Is it from the same problem.
Need help....pls