Need Help !!

Hey guys.. I recently got a custom made computer that my friend built for me and its great.. But there are still some probs that I cant figure out myself... Whenever I play any game it always kicks me out of it... Battlefield Vietnam for example.. It says that it encountered a problem and needs to close ? And Rise of Nations it just kicks me out ? What could be the problem ?? Ive updated all my drivers and BIOS... please help !

Here are the specs for it....

Motherboard:
CPU Type AMD Athlon XP-A, 2200 MHz (11 x 200) 3200+
Motherboard Name Asus A7N8X-E Deluxe (5 PCI, 1 AGP Pro, 1 WiFi, 3 DIMM, Audio, Gigabit LAN)
Motherboard Chipset nVIDIA nForce2 Ultra 400
System Memory 1024 MB (DDR SDRAM)
BIOS Type Award (05/20/04)
Communication Port Communications Port (COM1)
Communication Port Communications Port (COM2)
Communication Port ECP Printer Port (LPT1)

Display:
Video Adapter RADEON 9600 SERIES - Secondary (128 MB)
Video Adapter RADEON 9600 SERIES (128 MB)
3D Accelerator ATI Radeon 9600 XT (RV360)
Monitor Samsung SyncMaster 753DF [17" CRT] (HCCN809125)

Multimedia:
Audio Adapter nVIDIA MCP2 - Audio Codec Interface
Audio Adapter nVIDIA MCP2 - Audio Processing Unit (Dolby Digital)

Storage:
IDE Controller NVIDIA nForce 2 ATA Controller (v2.5)
SCSI/RAID Controller Silicon Image SiI 3112 SATARaid Controller
Disk Drive ST312002 6AS SCSI Disk Device (120 GB, 7200 RPM, Serial-ATA/150)
Optical Drive JLMS XJ-HD166S (16x/48x DVD-ROM)
Optical Drive LITE-ON CD-RW SOHR-5238S
SMART Hard Disks Status Unknown

Partitions:
C: (NTFS) 103998 MB (96689 MB free)
D: (NTFS) 10464 MB (10185 MB free)

Read the "how to post a question" sticky, your subject is pretty worthless.

Do you have software to monitor temperature? That is often a cause of system instability. Check that the heatsink is seated firmly on the cpu and all the fans are working.

Run memtest to check the ram, and get prime95 as a general stability check. Both should be able to run overnight with no errors. (Not at the same time).