Technically your PC is decent, could probably use a hard drive format since it's a tad old (going by the CPU being a Pentium 4), but I would increase the RAM to 3gigs and a video card upgrade, due to now knowing how big your case is, trowing a Geforce8 series car is out of the question.
Now WAR requirements are not that huge compared to other mmo's and games out there, but you do need a complete system upgrade at some point. The reason I say that is that the motherboard can only use socket 475 which has very little upgrade ability and can only use 4gigs of RAM capped, at the current state of gaming, 4gigs is the "optimal" for new games like AoC, Crysis and whatnot.
With technology changing so fast, good parts are actually becoming cheap, and Pwnzilla has made some good $500~ templates.
If you decide to simply upgrade what you have then you could use:
Kingston 1GB 240-Pin DDR2 SDRAM DDR2 667
Newegg.com - Kingston 1GB 240-Pin DDR2 SDRAM DDR2 667 (PC2 5300) Desktop Memory - Desktop Memory
$18.49
HIS Hightech H260XTP512DDN-R Radeon HD 2600XT 512MB
Newegg.com - HIS Hightech H260XTP512DDN-R Radeon HD 2600XT 512MB 128-bit GDDR3 PCI Express x16 HDCP Ready CrossFire Supported iSilence III Video Card - Desktop Graphics / Video Cards
$99.99
And also you might need fans for better air flow if your case doesn't have them already.