I volunteer at our Humane Society Thrift Store and redo the donated computers for resale. We just got an HP Pavilion a1130N with Windows XP Media Center Edition Version 2002. Processor runs at 2.19 Ghz, RAM memory is 1024 MB, hard drive is 225 GB. System works fine until I update to Service Pack 3 - then it will not start normally. I can start it in Safe Mode but it will not start normally or to last known good configuration. What is there about Service Pack 3 that could be causing this problem. Thanks for your help.