See here for a compatison: http://ark.intel.com/Compare.aspx?ids=29761,37255,
You will need ot check if it is teh correct socket and if so it may work, will on teh depend if the CPU string is in teh BIOS.
the T7500 should run a bit faster coz of the cache but will run hotter...
My dell is using the PM45 chipset and I think it'll fit nicely. What do u guys think? I've seen some benchmarks and it seems that the T6600 scores better than the T7500 on passmark benchmarking tool. Is it possible? Link: http://www.cpubenchmark.net/cpu_lookup.php?cpu=Intel+Core2+Duo+T6600+%40+2.20GHz
The t7500 cna have two different sockets according to ark.intel.com, therefore make sure it is the right one. And as i said will all depend if dell have in tehir BIOS the CPU ID string.