Video Card Upgrade Question

Hi all,

I've been thinking about upgrading my video card, maybe also my mobo/cpu because of a local store on boxing day sale! 5% off and some nice deals I don't know yet, that's why I need input from the pros! I am using the onboard mobo thingy card, which is pretty crappy already.. I am not a pro gamer, but I do enjoy gaming ;D I play some mmorpgs, 1st person shooters e.g. cs:s ;D

Here's a brief spec of my ancient computer: (almost 3 years old? around there)

CPU Type Intel Pentium 4 530J, 3000 MHz (15 x 200)
Motherboard Name Intel Avalon D915GAV (4 PCI, 2 PCI-E x1, 1 PCI-E x16, 4 DDR DIMM, Audio, Video, LAN)
Motherboard Chipset Intel Grantsdale-G i915G
System Memory 1504 MB (PC3200 DDR SDRAM)
BIOS Type AMI (08/24/05)

www.canadacomputers.com <-- that's my local store
Here's the card that's on sale, I don't know if it's good or not:
BFG GeForce 7900 GS OC nVidia GeForce 7900GS Chipset (525MHz) 256MB GDDR3 (1320MHz) PCI-Express Graphics Card 20 Pixel Shader Processor SLI-Ready Windows Vista Ready
$159.99 CAD

hmm i dun think my mobo/cpu meet the minimum requirements. i dunno will my mobo/cpu able use it efficiently or my computer might explode due to like super heating? I don't know much about computers D; Should I get a new mobo/cpu/video card all at once? If i do, do i need to change my computer tower, fan and ram and stuff too D; ? my spending range's around $300 CAD max total well 500$ is all i ahve in my bank a lil over it's ok, im poor university's drainingg my cash lol. Any suggestions of combos whatever

p.s. as u can tell, iam not too familar with computer stuff D; thanks in advanced! appreciate it!

 

the sales tomorrow! anyone? i dunno if my comp can handle that card, or should i just get a really cheap pci-e card
2 PCI-E x1, 1 PCI-E x16 <-- what does that mean?

 

hiyooo pci e x1 is for nic cards,firewire,sound cards and old video cards...pci express 16x killed agp8x cuz its 2x faster.pci e 16x are where the top of the line video cards r bro.