Dell Latitude D520 & T7200 Processor

Hi everyone out there. Hey, I have a Dell Latitude D520. I have been buying & selling processors for a while. I tend to purchase Dell Notebooks a lot. Here is what I ran into. I have a T7200 Processor. I put it in the D520 I have & didn't get any video or anything, since I had it listed for sale locally I sold it thinking I had a BIOS issue or maybe it just wouldn't work in this one. The person who bought it just called me & told me that there is something wrong with the processor. He said sometimes it run's for 5 minutes, 1 hour, 1/2 hour and so on. I asked him if he updated his BIOS. He told me he did everything with no luck. He's bringing it back this week for a refund. I made the mistake of not writing down the S/N so I wont know if it is the one I sold or not. My question is, does it sound like a bad processor or maybe incorrect BIOS settings. I don't know what model he has yet so I can't do any online research. He did say that the BIOS showed a T7200. He said he ran a stress test & that confuses me because if it is a bad processor how did he manage to do the stress test. Thanks, Dan, please note that my Latitude came with a Celeron Processor so I'm thinking it was the wrong one for the D520. Thanks again