the system in question is only about 9 months old. It has a Gigabyte MB 780 chipset running a Phenom 9550 x4 CPU, 3 GB's DDR2 800MHz RAM, PNY 9500GT, dual 19" LCD monitors, 500GB Hitachi sata2 drive, optical drive, Thermaltake PSU, backup drive, and wireless mouse/keyboard. There are actually 2 of these systems and the other one has never had any issues at all. the one in question will freeze up from time to time. Sometimes once every 3 days or so sometimes 2 times a day. I have replaced the MB, PSU, swapped out the RAM, the only things that hasn't been swapped is the graphics card, but usually a graphics card problem nets a BSOD or other obvious graphics related issues. Drivers have all been updates, voltages and temps have all been monitored and are within norms, BIOS has been updated and the usual suspects (viruses, malware, spyware) have all been checked for and have come up negative. I have noticed that at any one time there can be anywhere from 8000 to 15,000 emails in the inbox on Outlook 07. this system is heavily used in a business office and receives emails from fax, customers, spammers, & scans from an IP printer all day long. Outlook is almost always opened when the system is in use. Outlook is set to do a send receive every 5 minutes. I haven't checked the size of the .pst file, but I'm sure it's enormous. I've hit a brick wall. Could Outlook be the cause of the system locking up? system in question is running XP Pro 32bit SP2/SP3. Thanks for any help you can provide. Steve