Computing freezes when accessing the Internet

My Computer is freezing when I access the Internet, I am unable to raise Task Manager and therefore have to shut off manually using the on/off button
I have the following in my PC – AMD Athlon XP 2000+ 1.66Ghz processor, 512MB RAM (2x256) Ram PC2700 DDR -184 pin 333Mhz DIMM (32x64), Motherboard – Jetway V400DB/V400DBL, Seagate 60 GB hard disk, Virgin Broadband..
The problems started a week ago when I installed additional memory, I have three memory slots, I purchased 512 memory upgrade (1x512) this was placed in the first slot with the 2x256 placed in the second and third, the new memory is the same specification as the RAM already installed. Jetway instructions do no say that all slots have to contain the same amount of RAM and that the system will work as long as no more than 3GB of memory are installed.
I have been unable to do a System Restore under three separate dates but finally went into SAFE Mode to carry out this task which was successful.
Norton Protection Centre showed no problems when I ran a scan although I am unable to get any further updates due to the problem.
All other programs i.e. Word and Excel run perfectly
The additional RAM is shown in my Systems Properties
Any help would be appreciated

have you tried your computer without the new RAM just to confirm that this IS your problem?
you say it is the same specification... same speed aswell i presume? (PC2700)
have you checked for viruses/spyware?

If your computer works normally without the new memory in, try with the new memory on its own, and then with one 256mb, if the problem re-occurs, try the other 256mb

If the problem occurs when ONLY the new memory is installed, this will probably be your problem (either incompatibillity, a faulty slot or damaged RAM)

also try this test, un-zip it to a floppy, then boot your computer from the floppy... it will report any errors it finds (do this with the new memory installed)

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