So I'm Going To Build My Own PC

[Danked]

I bought my PC from ABS last April for about $1300. These were the specs. Out of everything on this list, what are the first few things you'd recommend I upgrade before anything else? Me not smart.

Raidmax Model 268WBP(BLACK/SILVER) 10-bay Case Retail No Power Supply (Item#ABS11156018) 1 Standard
Gigabyte GA-7VAX ATA133 AC97 Sound USB 2.0 8X AGP Motherboard (Item#ABS13128154) 1 Standard
Allied 400 Watt Power Supply with 2 Fans (Item#ABS17154013) 1 Standard
AMD Athlon XP 2600+/333 FSB 256K Processor (Item#ABS19103349) 1 $100
Dynatron DC1206BM-L/610-P-Cu HeatSink and Fan (Support Up to 3000+) (Item#ABS35114009) 1 Standard
*Corsair 512MB PC2700 DDR RAM (Best with Supported Motherboard) (Item#ABS20145407) 1 $40.5
Western Digital 120GB 7200RPM Hard Drive - 8MB Cache Special Edition (Item#ABS22144118) 1 $45
SAPPHIRE ATI RADEON 9500 PRO 128MB DDR DVI AGP (Item#ABS14102258) 1 $135
LITE-ON XJ-HD166S 16X DVD ROM Drive BLACK (Item#ABS27131603) 1 Standard
Lite On 52x24x52 CDRW Black Model LTR-52246 (Item#ABS27106190) 1 Standard
Sound Blaster Audigy Sound Card w/1394 Firewire Port (Item#ABS29102148) 1 $65
Creative Inspire Dolby 5.1 5200 5 Speakers w/Subwoofer (Item#ABS36116116) 1 $33
Aopen FM56-SVV V.92 PCI Modem - Retail (Item#ABS25131005) 1 Standard
Mitsumi 1.44 MB Floppy Drive - BLACK (Item#ABS21104101) 1 Standard
Mitsumi KFK-EB9HY-BK BLACK PS/2 Keyboard with Hot Keys - RETAIL (Item#ABS23133003) 1 Standard
none Input Devices 1 $-15
Multimedia Microphone with Base (Item#ABS36111104) 1 $0
ABS Mouse Pad 8" X 9" (Item#ABS17114103) 1 $0
Microsoft Windows XP Home with Service Pack 1 (Item#ABS37110010) 1 Standard
Corel Office WP 2002 (Item#ABS32106119) 1 $0