Hello, I started installing SP3 for XP this morning it appears to be stalled. It has not given me an error but has not moved for at least 3 hours. The update installation screen states: Please wait while setup inspects your current configuration, archives your current files and updates your files. Finishing installation. Running processes after install. It has been at this point all morning.

So long as your computer hasn't fallen asleep you may want to leave it on for a few more hours. Is the computer connected to the internet during the update? It may just be taking awhile if your computer is running slow.