Performance/Lag

[G. Martel]

Hello, I've been playing for two weeks now, today when i was trying to play MP, my "Performance" item was horrible, and my ping was getting betwen 1.2 and 2.5. When i started to play the lag didnt allow me to continue playing. finally i gave up, i decided to fix my pc but i dont know where the problem is, so here is the type of system i got, i worder if someone can tell me what's wrong with it, in my opinion is the memory RAM, but it can be someting else, thanks.

PC:
System: Windows XP.
Processor: Intel[R] Pentium[R] 4 CPU 3.00GHz.
Video Card: ATI Raedon 9550.
Sound Card: Sound Blaster live! 24-bit.
Memory: RAM 1 GB.

INTERNET:
Linksys Wireless-G PCI Adapter (54Mbps) (the main modem is in other room).