You have a T2341, right? My current rig (soon to be replaced, and my wife gets this one) is/was a W2040.
It still has the original case, PSU, CPU, and mobo. I added a DVD drive, then replaced the CD burner with a DVD burner. I replaced the original 128MB with a stick of 256, then added another, then recently swapped one of them for a gig. I replaced the 40gig hard drive with a 160gig one. I added an older graphics card (no need for a top end). Of course, I did all of this over three-four years.
if you don't have the cash to plop down on building a new rig, ad what you can.
You have a 2400+. You can look into a faster CPU (they go up to 3200+, and there are a couple of them for sale in the Buy/Sell/Trade forum).
You have 128MB of RAM (unless you have added some)... RAM is a quick and relatively cheap upgrade; 512 would make a world of difference, a gig is better.
A graphics card whips integrated graphics any day, and you have an AGP slot. Pick up an older graphics card for $40-$75 easy.
Hard drives have come way down. You can pick up a 160 gig one for less then $100.
There is always options.
My Rig: SABLE
Antec 300 Illusion / Antec EarthWatts EA650 650W / EVGA GTX 760 2GB
AMD FX 8320 x8 Black Edition / Gelid Tranquillo / MSI 970A-G43
Sandisk Ultra Plus 128GB / Samsung 840 120GB / WD Black 750GB / WD Green 1TB / WD Red 3TB
G.SKILL Ripjaws 2x2GB DDR3 1600 - Crucial Ballistix Tracer 2x2GB DDR3 1600
Win7 Ult 64-bit - Func MS3 Mouse - CM Storm QuickFire Rapid Mech Keyboard
R.I.P. Danny L. Trotter
... 14 Nov 1945 - 4 Sept 2009