Ubuntu problems

After installing Ubuntu on top of existing windows harddrive and enjoying it for a few days, it looks like I have to reinstall Ubuntu again. Somehow I messed up some boot variables, causing the computer to be unable to shut down properly. It either runs through a million lines of error code, or hangs on a certain step. It could also just be my harddrive, which I shipped to Montreal in my luggage. The hard drive's sounding louder by the day, reminding me to replace it. Plus, it's an IDE harddrive with 80G capacity. Ample for my use, but a replacement of 320G is not terribly expensive.