The other day a friend dropped her computer off to get us to fix some of her problems (BSOD, Viruses, etc). When I powered it up, the virus she said was on there, was not there. Still I removed AVG and installed Avast antivirus.
Avast displayed a message saying that we had a virus that attached itself to the boot sector and asked if we wanted Avast to remove it. I clicked yes and I got told that to do this I must restart the computer, so I did that and the Windows Vista boot diagnostic came up (this was not meant to happen) and tried to fix the problem and restarted itself, the boot diagnostic came up again! and it just went into a loop
I downloaded the Windows Vista recovery disk (64bit Download*, 32bit Download**) I unzipped the zip file and burnt the iso image to a CD. I put the CD into the computer, rebooted it and pressed a key when it said “press any key to boot from CD or DVD”, waited for it to boot then clicked next (don’t worry this will not wipe your computer or reinstall vista). Now click “Repair Your Computer” or press “R” on the keyboard wait for it to find your vista installation and click Next. Now click Command Prompt.
Now I type (into command prompt) “bcdedit /export C:\bcd_backup” and press enter.
Now we want to move to the directory “C:\boot” to do that type “cd C:\boot” and press enter.
Next you need to type “attrib bcd -s -h -r” and press enter.
Now we need to rename the bcd (just so we have a backup copy). Type “ren C:\boot\bcd bcd.old” and hit enter.
We can’t leave it like that as you would have no BCD! Now type “bootrec /RebuildBcd” and hit enter and type Y when it says “Add installation to boot list?”.
Close command prompt by typing “exit” and pressing enter or by clicking the X
Now press “Restart” and your computer should boot correctly!
Some of the steps are from this video