Need help reformatting Mini12 to deafault 8.04 Ubuntu

Hi, I've had my Mini 12 since Jan 09 and haven't had any problem too large until recently. I was cleaning out some files and deleted something that wasn't meant to be deleted which has left me unable to do anything with my Mini other than access Firefox through the Alt+F2 run application command. When I try to open any document or image on my desktop I receive an "Couldn't display "/home/(username)/Desktop/(nameoffile)" There is no application installed for this file type" error message and when I try to access any folders via the places menu on the taskbar I receive a "Could not open location 'file:///home/(username)/(pictures/desktop/etc.) error message. I've also been left unable to access the terminal.

I honestly have no idea what I could have deleted to cause this problem nor do I have any idea how to fix it and I've come to the conclusion that the easiest thing to do would be to just reformat and start fresh as I was able to move all the files I wished to keep to a thumb drive. When I came to this decision I had no idea how difficult it would be to figure out how to perform said reformat which leaves me where I am now. I wouldn't mind updating to a more recent version of Ubuntu (as long as its stable that is) as it seems that is now somewhat possible to do but my computer literacy is what I'd call slightly above average and I'd likely need to be walked through the process with some nudging as most of what I've read on how to do so has been a bit over my head.

Any help will be greatly appreciated and I look forward to reading your replies,

detodos

Cliffs: My Mini 12 with Ubuntu 8.04 is messed, badly need help in figuring out how to clean whipe/reformat