Well if your friend won't allow you to install your HDD as a slave in his machine to recopy files from his drive onto yours; but you do have some sort of "Online" backup service, it becomes a bit dicey.
Because :
1) The only way I know that you are going to be able to get rid of the "Sasser Worm" and get your HDD to boot is by formatting "C"; which will erase EVERYTHING on "C" drive.
2) You should then be able to reinstall "Windopes" on your machine, and have it boot normally; BUT you then have to either reinstall everything, or restore from your "ONLINE" backup.
3) Should you choose the latter, then there exists the possibility that you will get the worm back.
Me, I prefer to keep my own backups, (PLURAL), some older than others, so in the event of problems like this, I can go to an older backup.
Others here may be able to give you better advice.