General :: Computer Crashed After Updates - Multiple Flavors Of Installed ?

Trying to help brother whose computer quit working after he downloaded updates. Don't know Linux lingo but it looks to me like he has multiple flavors of Linux running: Gnome, ubuntu, xbuntu, kbuntu - probably more I've forgotten.

He knew nothing about computers at all and inherited a build-it-yourself computer kit that someone was throwing away. It came with a CD of Linux software. By trial and error he made it run and has managed to do some amazing things with photos and graphic design. But he downloads and launches EVERYTHING that suggests itself to him. Sometimes a thousand files at a time.

Now his machine boots but won't run any apps. It keeps giving him a message that he needs to "manually run" some "dpkg-something" but he doesn't know how to get to any sort of root or command prompt where he can enter a manual command. All he knows how to do is click icons. He's clicked them all. Now his computer is continually running screen after screen of programming language.

Is there any hope? Can we reinstall an OS without losing all of his files of graphics work? Which OS should he use on a fairly old and slow machine if his main (only?) use is graphic design?