The Intel 865 chip-set doesn't support DDR2.
They didn't introduce DDR2 support until the 915 chip-set generation.
Check out Wikipedia's info on it here.
Intel's info on the 865G chip-set's memory compatibility (specifically on the Intel D865GBFL board) is here:
The Desktop Board D865GBF has four
DIMM sockets and supports the
following memory features:
- 2.6 V (only) 184-pin DDR SDRAM DIMMs with gold-plated contacts
- Unbuffered, single-sided or double-sided DIMMs
with the following restriction:
Double-sided DIMMs with x16
organization are not supported.
- 4 GB maximum total system memory
- Minimum total system memory: 64 MB
- Non-ECC DIMMs
- Serial Presence Detect
- DDR400, DDR333, and DDR266 SDRAM DIMMs
Hope that helps.