Vertical Bars on my Screen (Driver Problems..?)

Hello guys,

I've got a problem and I need your help!

When surfing a month ago, 4 vertical bars appeared on my screen
( http://www.geocities.com/lorenzopelswijk/verticalbars.html )! After
restarting they kept reappearing. At first I
thought it was a virus, but after downloading Ad Aware and various
other virusscanners, nothing happened. Finally I bought Norton
Antivirus 2005 and still it found nothing..
So, I re-installed windows XP, but to no effect. Then I erased my C
drive. Nothing happened. Then I erased my other drive with all my
music, anime and other valuable stuff, but still the bars appeared!
After completely re-installing my computer the problem had remained!

But, I've found out that that the bars don't appear as long as I don't
install the driver of my videocard. Ati Catalyst. But then my internet
is all slow and crazy and I can't play any games without it. So I
downloaded the latest driver and various other, but still to no
effect. So what to do! My computer works just fine, but it really
sucks if your surfing or watching movies with 4 bars constantly on
your screen. I'm not a computerexpert, so don't asks me to look inside
my computer as I've never looked inside one nor know anything about
how it works. I've had my computer for 2 years and haven't had any
problems with it before. Does anyone know what the **** is wrong with
it? Please reply and deliver me of this evil inside my computer!

Here are my specs and by the way, I've still got warranty, but I'm
hoping
you guys will know what to do and come up with a simple solution!
Thanks in advance!

AMD Athlon XP 3000+
2.16Ghz
1GB ram
120 GB
RADEON 9800 PRO
128 MB
Windows XP

Do not double post.