I-Tunes not appearing + crashing system, no solution works so far

Question

General problem description
I-Tunes does not appear after program start, and the computer slowly crashes by other programs (explorer, MSN) all not responding anymore after a while
Sequence of problems
1. I start up I-Tunes from the program list
2. Mouse cursor changes to hourglass quickly, then back to normal
3. I get shown the license agreement (in Dutch, since I am Dutch).
4. I click on 'Akkoord' which is Dutch for 'Agree'
5. The cursor quickly changes to hourglass and back, but nothing further happens
Accurate Problem Details
ITunes.exe, Ituneshelper.exe and Ipodservice.exe all show up in the Windows Task Manager under 'processes'.
None of these programs show up under the 'applications' tab.
After going through steps 1-5, I can access some programs normally, but as soon as explorer or any aspect of it is accessed (such as saving a file in Paint Shop Pro), that program or explorer itself stops responding and crashes.
When I try to reboot my system, it shuts down all the crashing stuff (explorer etc). However, it also shows what I think is I-Tunes as 'not responding'. It has the I-Tunes icon, but the title is all garbled. Presumably, this is the I-Tunes program crashing. The computer won't, in fact, reboot, and just stands still.
Quicktime itself runs fine, and I have no problems with any other programs or instability.
Having my I-Pod Nano 4GB connected or not makes no difference, the crash is the same.
Tried Solutions
I searched the forums and help files for solutions - here's what I've tried so far:
- Uninstalling all Quicktime and Itunes programs, cleaning all files associated with them, using Windows Install Cleanup afterward, and then doing a clean re-install. No result, same problem
- Creating a new 'user' in Windows and running I-Tunes from there. No result, same problem. Crash is the same even when reverting back to the other user.
- Cleaning the I-tunes preference files, hidden files, system32 files etc, no results.
- Uninstalling and completely removing I-Tunes and Quicktime, installing a stand-alone Quicktime, then I-Tunes. No result, same problem.
- Installing AVG anti-malware software and scanning for malware. Nothing found. No result.
- Using an older version of I-Tunes, same problem, no result.
Thanks in advance
Any help from anyone would be very much appreciated. I cannot access my I-Pod nano right now, and have no idea how to get to it.
AMD Athlon 64 X2 Dual Core 3800+, 2gb RAM   Windows XP Pro  

Answer 1

ITunes.exe, Ituneshelper.exe and Ipodservice.exe all show up in the Windows Task Manager under 'processes'.
When I try to reboot my system, it shuts down all the crashing stuff (explorer etc). However, it also shows what I think is I-Tunes as 'not responding'. It has the I-Tunes icon, but the title is all garbled. Presumably, this is the I-Tunes program crashing. The computer won't, in fact, reboot, and just stands still.
a preliminary question. do you have Norton Internet Security 2005 installed on that PC? i associate those symptoms with the nastier versions of NIS-2005-related itunes launch failures.