blue screen on start-up

Hello, I have a problem with my Dell computer where on the start up it comes up with a blue screen saying:

stop: c000007b bad image. The application or dll \??\c:\windows\system32\sfcfiles.dll is not a valid windows image. Pleace check this against your installation diskette

This probem started when I wanted to do a disk defragment. It came up saying that first I needed to do a chkdsk thing. So I tried to do that and it said I had to restart the computer to make it run. So I did that, it did the chkdsk thing and then went to the blue screen with the error.

Each time I turn my computer off and back on, windows starts loading up, then it gives the option of doing a chkdsk, or pressing any key to continue. So I either do the chkdsk, and that runs for a few minutes and goes to that blue screen, or I press any key and that goes to the blue screen.

Also, I have tried going into safe mode on start up to try to fix the problem and to back up important files. A big list comes up on a black screen with a whole lot of lines with the last line being....

multi(0)disk(0)rdisk(0)partition(2)\WINDOWS\System32\Drivers\mup.sys

So I need some help in resolving the problem, or even in being able to back up important files if this can be done without safe mode. Thanks.

Let me know if more info is needed.

I run Windows XP Media centre edition.

Thanks

I am also using dell and i got the same problem previously try to re-install your Operating system or the crack file is missing for sure it will help i think so if there is no other reason without that.