I work in the IT dept and I have always picked up the ones they have recycled out. Usually, I fix the ones that need a little TLC and re-purpose them for family members and friends who are needing a laptop, but don't require the latest and the greatest.
I have two more Dell D630's that have the Vista COA, and I found out that I can just switch the hard drives with Dell D620's and update a driver or two, and we're good to go. The D620's were shipped with the XP COA. I'm going to talk to my step-dad to verify which model I gave him, and if it's the D620, I'm going to set him up with a D630 and turn in the D620.
I also unloaded whole bunch of working and non-working OLD HP 6120's to a friend of mine so he can sell them as parts on his eBay store. I'm going to get with him and see if we can piece together 2 or 3 working laptops for the trade in.