They are both Core 2 Duo. Both are 2 GHz, both have 2MB cache. Only difference is FSB 667MHz for T5750 and 800 MHz for T5800. T 5800 also might be newer stepping. Given the choice I would go for T5800.
No, the Pentium Dual-core and the Pentium D ARE NOT synonymous, they're not even based on the same core (The Pentium Dual Core is based on Allendale and Wolfdale, the same core the E4000, E6000, E7000 and E8000 series are based on).
In short, the Pentium Dual Core is the same thing in essence as the Core 2 Duos, just with less cache and a slower FSB. Circuit City mislabeled the processor, both processors are Core 2 Duo T5800, so you're looking at the exact same processor in each computer.
I havn't looked into other specs. Was just looking at CPU's. I real world there will be no noticable difference between CPU's. I some tasks T5800 might be sligthly better. Look at the other specs and price don't worry about Cpu if choice is between theese two.
I bought a Medion P6612 note book. It keeps crashing (only Three weeks old) comes up with blue screen of death. Comes up with memory_management or apc_index mismatch, it has a core 2 p7350 2.9GHz,£MB L2 Cache,1,066 MHZ FSB . Should I send it back (I can get a full refund trough ALDI if under 30 days) and buy over Christmas? . I mostly use a computer for the internet ,photos and digital video and email.I do not do much word,excel etc.