Jeg kan ikke se hele siden.

hmm you should get the latest version of Internet Explorer.
And/or the latest update for XP.

I have both off those things, I formated all 3 pc a month ago and installed the same XP and updated the all

go here to find the updates you are missing:
http://v4.windowsupdate.microsoft.com/en/default.asp
Only install those that are "critical"

hmm it sounds strange
I guess that's why nobody answerede your question.
- nobody in here has got the solution.

no critical updates for me to get, and yes I agree with you this is strange 2 comp. are fine but mine isn't and I didn't do anything diffrent when I installed XP on my comp.

1st of all, many of those ads are MacroMedia Flash-animations. It could most certainly be the cause... Get newest versions of Flash & Shockwave-players:
http://www.macromedia.com/shockwave/download/download.cgi?P1_Prod_Version=ShockwaveFlash&Lang=English&P5_Language=English (Flash)
http://sdc.shockwave.com/shockwave/download/download.cgi?P1_Prod_Version=Shockwave&Lang=English&P5_Language=English (ShockWave)

2nd, are you sure you haven't allowed for some ad-stopping procedure? Most likely the HOSTS-file would be changed; C:\Windows\System32\drivers\etc\hosts - textfile with no extention (can be opened thru Start -> Run... typing "notepad C:\Windows\System32\drivers\etc\hosts" (w/o the "" and + enter ofcoz)). This is how I block almost all ad servers on my xp. Haven't bothered with a popupstopper, and I always respect locally hosted ads, but I keep a well updated hosts file to save my bandwidth for better things.

A blank HOSTS file looks like this, for reference:
[EXAMPLE]
# Copyright (c) 1993-1995 Microsoft Corp.
#
# This is a sample HOSTS file used by Microsoft TCP/IP for Windows NT.
#
# This file contains the mappings of IP addresses to host names. Each
# entry should be kept on an individual line. The IP address should
# be placed in the first column followed by the corresponding host name.
# The IP address and the host name should be separated by at least one
# space.
#
# Additionally, comments (such as these) may be inserted on individual
# lines or following the machine name denoted by a '#' symbol.
#

127.0.0.1 localhost

[/EXAMPLE]

:) hope some of all this helps

HMMMM I didn't quite consider that one I guess, hope it's not a direct copyright infringement!! Wasn't meant to be, anyway =)