Hi,
I have asked a couple of our moderators to take a look at the options available to you.
The conclusion is:
1. - borrow a disk that has SP1 on it and do a repair install. I suspect that this is unlikely - is it ?
2. - Remove SP1 and use your own disk ( the OEM one ) to do a repair install.
Take a look here.
click here
We came to the conclusion that we were not prepared to trust the version that you had downloaded and you were better working from the disk used to install the OS in the first place.