Upgrade the current computer, or buy a new one?

[jedi]

I bought my computer a couple of years ago, and was going for inexpensive, basic stuff to play poker on. Now the computer is running a little slow, I'm guessing partially because I'm multi-tasking on it so I'm trying to see if I need to upgrade the computer, or just get a new one. Now that I've made some money with poker, it might be time to spend it.

Current setup

Dell Dimension 2400 running Windows XP 2002
Celeron Processor 2.4 GHz
256MB RAM
74GB Hard Drive
1 monitor. (CRT)

I'm thinking at the minimum to get some more RAM, but a new monitor would be nice (reading about your 2001FPs). But if I start doing that, should I just get a new computer?

-Jedi