My PC stopped responding at a normal spe...

How long ago was this update? If it was recent say less then a week then you might be able to use system restore to put your computer back to working condition. To use system restore you have to know the date that the computer was updated then restore to sometime before that date.

Here are two ways to access system restore on windows xp. You only have to do one of them.
Through Help and Support:
1.
Click Start, and then click Help and Support.
2.
Under Pick a Task, click Undo changes to your computer with System Restore.
3.
Follow the instructions on the wizard.
Through the All Programs menu:
1.
Click Start.
2.
Point to All Programs.
3.
Point to Accessories.
4.
Point to System Tools.
5.
Click System Restore.
6.
Follow the instructions on the wizard.

just do a system restore to just before the update took place should solve the issue. if you need further assistance of how to do a system restore please state your version of windows that you are using.