I have an older Dell Inspiron, and I found out that I could double the memory by adding a supplementary card. Check your documentation and see if you can also double the memory.
This is not (at least for my Dell) a standard memory stick, but one designed for the Dell laptop. That will not speed up everything, but it should speed up some complex programs. I also
upgraded the hard drive, which has nothing to do with speed, but now I could put several OSs on it to test out. Your hd might be big enough already--mine was only 60GB.
I think the Dell is a nice machine, with a decent keyboard for a laptop and a good display. Using it at home, I connect an external kb (an IBM from the year 1 with a ps2 to USB adapter)
and a trackball, both via a USB 4-port hub. When I do that, I have to momentarily disconnect the kb on boot, or it won't see all the keys.