I purchased two new HP's (2.53 MHZ) , and put in video graphic splitter cards (Radeon 7500). Sometimes the cursor is unreliable. Either it seems to get stuck, bouces backwards, or disappears to the bottom of the screen. The mice are light-based (correct term?) so it's not an issue of the roller ball. Plus, it happens inconsistently. This is really annoying and I'm hoping it's not the computer as they charge a restocking fee. I've blown $8,000 on computers the past week and this is starting to really piss me off. I do now have 9 computers, including 2 laptops, so I can at least "get out of the office" on one side of my house and go to the "office" on the other side of my house. At least it's some form of exercise.