When I start my computer up, everything goes fine until suddenly my computer restarts, then it goes fine but restarts... This has happened before and it did go away but it's doing it again.
My physical memory is also random, its normally way over 256 MB but now its down to like 40 MBs.

OS: Microsoft Windows XP SP1(don't know how to get SP2)

Recent Programs/Drivers installed:
Sony Acid(uninstalled)
Syntrillium(uninstalled)
Orion VST(uninstalled)
Right-click My Computer and open the PROPERTIES. Under the General tab what is the Processor speed and how much RAM does it SAY is fitted?

When the computer is re-booting tap the F8 key to go into safe mode. In the control panel go to System, Advanced, Start up & Recovery Settings... and Uncheck 'Automatically restart'.

Next time the computer fails you should get an error message showing on the screen.

Take careful note of it and post it here.

Run a memory disgnostic such as MemTest86 overnight and see if there are any errors being reported.

If there are then try re-seating your RAM module(s).

Make sure that you take proper anti-static MEASURES before touching any internals.

XP Clean Installing
XP Compatability Test
XP Partition Management
XP Installing Recovery Console

RAM Knowledge Base
RAM And What it Does
RAM Virtual Memory Paging
RAM Reseating & Fitting PDF File

Processor Temperatures
Service Pack Slipstreamer
Power Supply Wattage Calculator
Everest Home Edition Computer Diagnostic Program

EmpTemp
CCLeaner

User  Profile Hive Cleanup Service

ERUNT-NTREGOPT

Microsoft Windows Malicious Software Removal Tool

TERABYTE

Powertoys/TweakUI

What does the events log report.

start /settings control panel

admin tools.