As you describe the problem, you attribute the freeze/shut-downs to Internet Explorer.
And it might very well be a problem of corrupted files in your IE.
At this point, I can't say one way or another if it is or isn't.
You could certainly attempt to uninstall IE 8, which will roll you back to either IE 7 or IE 6
Here's instructions:
http://support.microsoft.com/kb/957700#stepsforadv2
Steps for Windows XP or for Windows Server 2003
Click here to view or hide detailed information
Important You cannot uninstall Internet Explorer 8 if it is set as not removable. This occurs if you install Internet Explorer 8 before you install Service Pack 3 (SP3) for Windows XP. If this scenario applies to you, then you must uninstall SP3 before you can uninstall Internet Explorer 8. For more information about this issue, click the following article number to view the article in the Microsoft Knowledge Base:
950719 You cannot uninstall Internet Explorer 7 or Internet Explorer 8 after you install Windows XP Service Pack 3
To uninstall Internet Explorer 8, follow these steps:
1. Close all programs.
2. Click Start, and then click Control Panel.
3. Click Add or Remove Programs.
4. In the list of currently installed programs, click Windows Internet Explorer 8, and then click Remove.
Note If Windows Internet Explorer 8 does not appear in the list of installed updates, try the alternative steps for Windows XP or for Windows Server 2003 .
5. Follow the instructions to uninstall Internet Explorer 8.
6. When the uninstall program is finished, restart your computer.
If that solves your problem, you may wish to re-install IE 8 freshly, or may prefer to continue with IE 7 (I don't recommend staying with IE 6)
Alternatively, do you have another Browser such as Firefox, Chrome, or Opera?
If you do, do these browsers function without problem?
If all browsers cause freeze/shut-down, then we may be dealing with a more basic problem.
Since you've recently had an infection and removal of infected files, some of the XP operating system files may have gone missing or become corrupted.
Consider running System File Protection - System file Checker
from a command prompt type:
sfc /scannow - then press Enter
You may need your XP installation CD to complete the sfc scan.
You may also benefit from the disk scan tool to repair any file structure problems.
From a command prompt type: CHKDSK /r - then press enter
You will be warned that CHKDSK /r cannot be run because files are in use, and you will be invited to run CHKDSK /r upon rebooting your machine.
Agree typing "Y" for yes, then reboot.
Beyond the above, we may be dealing with a corrupted video driver or other driver.
Or we could find that the problem is hardware related.
Please complete the routines recommended above.
If no solution is resolved, post back so that we can explore additional steps.