@hell_storm2004, I've got a 2.20 GHz Pentium Dual-Core T4400 and 4 GB Memory running on my inspiron 1545.
I plan on upgrading to an Intel Core 2 Duo with 8GB Memory. <-a lot of people say the 1545 doesn't support anything more than 4 GB buuuut crucial.com says it's possible...so I'm going to take their word for it.
@saint19, I believe that it is actually possible with the dell inspiron 1545. I've seen youtube videos of people replacing the RAM and CPU. here they are: