Replacing laptop processor

I have never done this so I don't know if this is even possible, but my roommate wants to get more performance out of his Dell Inspiron 600m laptop. We looked at CPU-Z and his chipset is an i855PM, and his processor is a Pentium M 745. We were looking at the Pentium M 780 and Celeron M 585, would these be socket compatible, and best for his socket? Which would give the best performance? The programs he wants to run are Visual Studio, SQL Server, SAP Frontend, NetWeaver Developer Studio, and Photoshop.

Its possible but it has to be a 400fsb chip of the i855pm chipset and make sure the laptops bios is current before you swap them out.

Trap05 said:

Its possible but it has to be a 400fsb chip of the i855pm chipset and make sure the laptops bios is current before you swap them out.

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Thank you, what would be the fastest chip with those specifications?

http://www.intel.com/products/processor_number/chart/pentium_m.htm?iid=pn_ov+list_pmp

Pentium M 765 2.1GHz 400fsb - If you can find one expect to pay a lot and not gain much