There are two important points about which Core2Duo CPUs can be used:
1. socket 'M' (not 'P' or other variants sold with the same type)
2. FSB speed 166 MHz = 667 Mt/s (not faster or slower, as it can't be set in BIOS)
This leaves few choices (the 'T' and 'S' identifiers are on the upper label):
- T5500 / SL9SH or SLGFK or SL9U4 (all 1.66 GHz)
- T5600 / SL9SG or SL9U3 (both 1.83 GHz)
- T7200 / SL9SF (2 GHz)
- T7400 / SL9SE or SLGFJ (both 2.17 GHz)
- T7600[G] / SL9SD or SL9U5 (both 2.33 GHz)
The 'T7' ones are preferable because of 4 MB L2 cache (others offer 2 MB) - clock speed is less crucial.
I didn't test all CPUs, got data from spec lists.