I read your other post that RichieUK helped you with. Let's try the following:
1) Update your antivirus definitions and antispyware definitions. Do NOT run any scans yet.
2) Download CCleaner from www.ccleaner.com and install the latest version - make sure you UNCHECK "Install Yahoo! toolbar" unless you want it. Do NOT run it yet.
3) Boot to SAFE MODE without networking (tap F8 when computer starts).
4) Now, open CCleaner. On the "Cleaner" tab on the left select the Windows tab. Check all that is there EXCEPT the Hotfix Uninstallers, do NOT check that. Then, select the Applications tab, check all that is there.
Now, click the OPTIONS tab then click Advanced. UNCHECK "Only delete files in temp folders older than 48 hours".
Back at the Cleaner tab, select "Run Cleaner". Please be patient while your computer is being cleaned of temp folders, history, etc. Close CCleaner when done.
5) Run a full antivirus scan of your system. Do the same for your antispyware. Delete everything it finds.
6) Reboot into normal mode.
7) Check your firewall settings and see if IE7 is somehow blocked with accessing the internet. If it is, please allow it as your previous infections may have changed this setting.
8) Try IE7 now. If it still doesn't work read on.
9) Check your router to see if there is an update for the firmware...please update if need be. Try IE7 again. If no joy, read on.
10) Disable all your realtime protection including your firewall, antivirus, antispyware and any Spy Sweeper shields you have. Try accessing IE7 now. If it works, then re-enable each protection mode one at a time to find a culprit. Once you find the culprit try uninstalling & re-installing the application. For Norton, make sure you use the removal tool found here:http://service1.symantec.com/SUPPORT/tsgen...005033108162039
and then re-install Norton.
11) After all these steps, if you still cannot access the internet using Internet Explorer, try and repair install of XP. If you don't have the CD then try the instructions in this link:http://ask-leo.com/i_dont_have_an_installa...i_need_one.html
Make sure you backup all your data, emails, files etc. before doing this, just in case. You will need to re-install all your Windows Updates and you will be back to IE6. Make sure IE6 works then upgrade to IE7.
You may also want to download this "lifesaving" tool to back up your registry in case of problems.
Use the LEFT column and download the program. Install and run. There is an excellent readme file for this program in the install package to help you.
Good luck, let me know how it turned out.