Windows 7 Hangs At Starting Windows

Alright, so up until a few days ago, my computer had been running windows 7 professional 64bit without a snag, however I believe I was infected with a virus that has infected the MBR (Master Boot Record) sector of my hard drive, as well as my main windows partition. The symptom that my pc experience was that everytime I tried to load windows, it would come up to a screen asking me to either do a startup repair or to load windows normally. Loading windows normally resulted in the computer hanging at the "starting windows" screen, with the windows logo failing to popup. Preforming the startup repair took me to a screen with a white progress bar that would load completely and then also hang.I booted to my install disk, replaced the MBR through the control panel, and was able to boot to windows again, but a few restarts later the same problem has occurred. However, now booting to the install disk also hangs at the "starting windows screen" just as booting to a hard drive partition does. I have disconnected the SATA data and power cables to both my hard drives so the comp sees no imput from them, but when I boot to my install disk it STILL hangs at the "starting" windows screen.