ok, i am not a nick burns computer guy so give me some slack here.
i am using and old briggs 'n' stratton throwaway computer...it looks like a HP Vectra VE Pentium II 350mhz, running windows 2000.
it's worked for 2+ years now, with just a few problems, all software related i guess. (like IE and Outlook crashing)
now that i have thunderbird and firefox, things are getting pretty slow with this old boat anchor.
is there anything i can upgrade to make this thing faster? like get more RAM or something like that?

PS i don't want to get a new computer because this one has all the shit i like:
cd burner
zip drive
speaker hookups
usb hook up
nice coating of dust
real shitty looking so no one steals it.

You're platform is old enough you couldn't put a processor in it much faster than 500MHz. It's probably time to think about newer hardware. You could upgrade to an N-Force Motherboard, which would come with audio and video hookups, a nice cheap looking case/psu, and salvage the zip and CD-Burner from your old computer. It would be about as cheap as you could go.

If you're looking at the software alternative, linux is always there. Although this post might seem like an obligatory endorsement of the OS, you could see a benefit in performance. Picking an easy distribution of linux, such as Redhat, SuSe or Ubuntu would be nice. Having elder hardware almost guarantees compatibility and automatic detection of your hardware. Arguably you could make any of those persuasions of linux just as inefficient as your existing setup, so that will require more research on your part. You can create an efficient system for yourself with linux is my main point.

If linux is not in the field of possibility, you're gonna have to make a decision of at what point you want to freeze the software. Constantly upgrading the software components will simply kill you. Reducing unnecessary software and running regular maintenance like scandisk and disk defragmentation is the best deal for that.