Hi,
You may not have to replace your old computer.
The biggest, cheapest boost you can give an ageing computer is more RAM.
2GB is tiny by today's standards.
I use GKrellM
to watch the free memory, swap usage and swap rate, and disk I/O rates.
When your computer is running slow, look at the little graphs to see which resource is slowing things down.
Then you can make informed decisions about what needs improving.
Keep away from swap! Avoiding re-reading from disk using memory buffer caching.
CPU speed, RAM size, disk size etc have been following Moore's law and getting better all the time,
but disk rotation and seek times have not.
Ideally, you want to read some file in from disk _once_ after you boot, and not have to re-read it if you run that program again.
For example, if you use DDR2 RAM, add a 4GB kit for $56
Or, if you use DDR3 RAM, add a 4GB kit for $32
===
If buying a new computer, give it at least 8GB DDR3 for $62.
If you feel the need for speed, you could put your root partition on a SSD,
or use a motherboard that uses a SSD to transparently cache a normal disk.
You shouldn't be swapping, so don't put that on the SSD :-)
John