I'm new to this whole thing and although I have figured out my Canon GL2 pretty well, I'm now in need of advice about Post-production. I have a PC (an E-Machine) and not too much spare money. However, I would like to get some decent software because I am serious about making a short film. Any advice?

Take a look at the upcoming vegas 5!

http://news.sel.sony.com/pressrelease/4483

If you are short on money but want to get started then have a look at Avid's Free DV (http://www.avid.com/freeDV/index.asp). It gives you pretty basic functionality but is plenty to get going and good for long form work that isn't effect heavy.