IF SP3 for Windows XP is loaded on a system like a Compaq that has an AMD processer it is very likely that the system will not boot into windows normally after the install. If this is the case then follow these instructions to edit a registry key.
1. Press F8 while system is booting to get a boot menue to come up
2. Select “Safe Mode” from the list and hit “enter”
3. Log on to any administrative user account
4. Click “Start” then “run” and type “regedit”
5. Navigate to HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesIntelppmStart
6. Change “start” value to “4”
7. Close registry editor and reboot machine
System should now boot into Windows normally