Windows 7: Computer fails to boot into windows after sp1 installation

i've had some issues installing sp1 (7 ultimate, latest windows updates) via windows update when the installation fails on a few different error codes, but i have gotten it to install a few times.

each time the installation finishes, i restart the computer when prompted and it goes through the update process when shutting down, then after the windows 7 splash screen ("starting windows") passes, the screen goes blank (black screen, no video- monitor displays "going to sleep" message) and the HDD light on the computer is lit solid.

i've left the computer sitting for hours with no change- i eventually get Windows to boot again by using the install disc to do a Windows restore, but i haven't been able to get past this yet.

does anyone know what might be causing this?



any help is greatly appreciated.

thanks!

post any and all exact error codes/messages that you do receive before/during/after the install.

I might start with the following in order...
I can not tell you if these will work, chances are that it will not, but it is worth a try none the less.

1.) chkdsk

2.) sfc /scannow

3.) defrag