Vista - Display issue

I'm having a random display issue with Vista. Every few hours my display
stops working and everything moves randomly around the screen. I can
alt-ctrl-del and select reboot and contine. Anybody know why this is
happening? Another week of this and I'm going back to XP.

I'm using Business edition:
Component Details Subscore Base score
Processor AMD Athlon(tm) 64 X2 Dual Core Processor 3800+ 4.8
Memory (RAM) 2.00 GB 5.9
Graphics NVIDIA GeForce 7600 GS 4.2
Gaming graphics 751 MB Total available graphics memory 4.5
Primary hard disk 125GB Free (139GB Total) 5.3
Windows Vista (TM) Business

System
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Manufacturer Dell Inc
Model Dimension E521
Total amount of system memory 2.00 GB RAM
System type 32-bit operating system
Number of processor cores 2
64-bit capable Yes

Storage
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Total size of hard disk(s) 149 GB
Disk partition (C 125 GB Free (139 GB Total)
Disk partition (D 6 GB Free (10 GB Total)
Media drive (E CD/DVD

Graphics
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Display adapter type NVIDIA GeForce 7600 GS
Total available graphics memory 751 MB
Dedicated graphics memory 256 MB
Dedicated system memory 0 MB
Shared system memory 495 MB
Display adapter driver version 7.15.11.65
Primary monitor resolution 1680x1050
Secondary monitor resolution 1440x900
DirectX version DirectX 9.0 or better

Network
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Network Adapter Broadcom 440x 10/100 Integrated Controller
Network Adapter Microsoft Tun Miniport Adapter
Network Adapter Virtual Machine Network Services Driver