TP35D2-A7 needs bios update before it can use an E8400. I just purchased this combo. I could not find any clear details if the CPU and motherboard would work together. Several user reviews on newegg.com and posts on some over clocking boards indicated they work with each other. When I powered up my machine for the first time I discovered they don't work out of the box.
Intel Core 2 Duo E8400 Wolfdale 3.0GHz 6MB L2 Cache LGA 775 65W Dual-Core Processor
BIOSTAR TForce TP35D2-A7 LGA 775 Intel P35 ATX Intel Motherboard
The power supply would turn on, all my fans would spin up, and then they would all spin down. Power would recycle and it did the same thing over and over. I looked to the manual for the TP35D2-A7 and it indicated 2 LED status lights were on the board. Neither one lit up and that indicated unusual mother board or CPU issue. In the over clocking section of the manual it indicated the power would cycle like I was seeing when clock settings did not work with the CPU.
I was reading on the Biostar page and it does not list the E8400 as a supported processor. In the FAQ they had a question on support for the 45nm processors and it indicated a bios update was needed. I saw this before I made my purchase. When I ran into this issue, I expected that I needed to do a bios update. The catch is if you need a supported processor installed to update the bios. If this was my first build and all I had was the E8400, I would have been dead in the water. That was my situation.
I work in an IT department so I took my computer in with me the next day. I used a processor from a work machine to get it to boot up and flashed the bios. I placed the E8400 back into the mother board and it booted up without issue.
To sum it up, you will need a bios update for TP35D2-A7 if you are going to use an E8400 with it and you need a working processor to update the bios. I was using the E8400 but the same should hold true for the E8200.