I am a total beginner so please take that into account...

I wiped an old dell optiplex sx280 and put 12.10 (I think) on it and it was working fine.

It wanted to update and I said yes, it installed and required a reboot but ever since I get the message I am running in low graphics mode and I can't get past it or get it to boot.

I have video files on the desktop I want, if I can get to them and save them to an external hard drive I'll just reinstall from a boot CD but I'd rather not lose the files.

Any step by step help would be greatly appreciated.