After installation, Windows won't start up.

I had windows 7 installed on my machine and because of a virus infection, I had to format my C: drive and reinstall the operating system.

The disc seems to install windows 7 fine, but then when I go to start windows, nothing happens. The 'starting windows screen' appears but then it just leaves a blank black screen with the mouse cursor.

I tried again with all external usb drives/cams taken out and also ran a memory diagnostic, but it didn't help.

What could be the problem?

You need to wipe the HD of all infected code: SSD / HDD : Optimize for Windows Reinstallation

Then follow these steps to get a purrfect reinstall: re-install windows 7

If it still fails, test the HD with maker's diag/repair extended CD scan: http://www.carrona.org/hddiag.html, followed by Disk Check run from the DVD Repair console Command Line.

Okay thanks very much. I tried deleting the virus using the hard drive scanner then I tested it with installing a previous version of windows XP and it worked perfectly fine.

So I believe the virus is completely gone, but I been windows 7 for the network drive and extra large storage hard drive

I tried installing it again, but I'm stilling getting the blank screen.

It might be a problem with the disc as it was a priate copy, but it worked fine over a year ago when I first got the computer.

Buy a copy of Win7 to get a reliable installer.

If you already have a legit key to activate it, then borrow a DVD or find another ISO, rightclick scan with AV and Malwarebytes, then burn to DVD using ImgBurn at 4x speed, or write to flash stick using UltraISO trial version.