Build your own, I would never recommend buying one if you can build it..use RDRAM if you are going with a P4. They didn't get many of the bugs out until the 1.7 so don't get anything before that. If you are starting from scratch you can go with XP. If you are going to use older hardware go with 98se or just do a dual boot with 98se and XP. The problem is with the drivers/hardware more than software when it comes to XP. If you click a software's icon and go to Properties>Compatiblity it should solve any older hardware issues.