I told you my opinion, If I was in your shoes I won't upgrade the CPU.Professionals do not do works against Factory specifications, and I fixcomputers for living.
Acer says Pentium dual is not supported on Acer 4315, I can only tell you not to do such an upgrade.
Itwould be the same as if you ask me if you can mount a Jaguar engine ona Mini, yes, for sure there is the way to mount it, but the car won'twork as it is supposed to, and risk to blow at first corner.
If you really want to replace your CPU consider the following.
Acersays pentium 2 dual core is not supported on 4315, if you do ityourself you risk to damage the computer. Do not do the CPU upgrade ifthis is your only laptop, or if you care of this laptop, chance ofdamaging laptop are high. This kind of upgrades are done more as anexperiment.
I know Core 2 Duo T5300 1.73 Ghz had been installedsuccessfully on Aspire 4315, Acer says not to install any core duo, Iknow for sure Pentium duo T5200 1.6 Ghz works on Aspire 4315 with noneed for replacing cooling system.
Both chipset are difficult to find, best place to find them is Ebay.Check this link for an extensive report on this matter:
check also: Is it worth upgrading the CPU on Acer Laptops?