Boot-up problems

Hi
First of all, I'm running Windows XP (Home Edition, I think) with SP2.
A couple of days ago I installed a Microsoft Update - Malicious Software Removal Tool. As it was via the Microsoft Automatic Updates thingy I thought it would be a good thing to have. Since installing it, I've been having problems booting my computer and today I can only boot into Safe Mode. When I try just booting
I get the Windows XP Logo with the moving bar underneath, then the screen goes black, hangs for a minute and then the computer starts the reboot sequence. From there I can boot into Safe Mode only (and that only seems to work for a little while before the colours go funny).
I have tried System Restore (to a point before the Automatic Update) but that has not helped at all. I've also tried hoovering out the dust from inside the computer and adding another fan (to rule out overheating problems) but that has done no good either.
I'm about at the end of my tether (using my son's laptop to post this) so if there's anyone out that that can help, you have no idea just how grateful I will be.
(This is how I feel at the moment - banging my head on a brick wall!!)

Malicious Software Removal Tool downloads, runs, and then just goes away (assuming nothing's found) so is that because it found something and remove it causing you all this trouble?

I have no idea - and I don't know what to look for. I did see in another forum I looked through that if a device is listed more than once in Device Manager, that can cause problems so I checked.
In Network Adapters where I used to have two items listed, there are now 14 (fourteen!!):-
Direct Parallel
NVIDIA nForce MCP Networking Adapter
NVIDIA nForce MCP Networking Adapter Packet Scheduler Miniport
NVIDIA nForce MCP Networking Adapter Radial Miniport (X86)
Realtek RTL8139 Family PCI fast Ethernet NIC
Realtek TEL8139 Family PCI fast Ethernet Packet Scheduler Miniport
Realtek TEL8139 Family PCI fast Ethernet Radial Miniport (X86)
WAN Miniport (IP)
WAN Miniport Packet Scheduler Miniport
WAN Miniport Radial Miniport (X86)
WAN Miniport (L2TP)
WAN Miniport (PPPOE)
WAN Miniport (PPTP)

I believe the WAN Miniport has something to do with Firewire (wireless internet connection?) and/or AOL. I have cable broadband to a wired modem and have never had anything to do with AOL so how these are now on my computer is beyond me. I also do not remember the Direct Parallel one being there before either. What is the Packet Scheduler Miniport and Radial Miniport (X86) all about? Again, they were definitely not there before.

In System Devices "Motherboard Resources" is listed three times, and "NVIDIA nForce2 Memory Controller" is listed five times.

I'm sorry this is such a long-winded post but I wanted to get as much info across as possible. Do you think this could be the problem and if so, is it safe just to delete the extra ones?