Primarily interested in CPU upgrade at this time. I downloaded CPU-Z to determine my specs, and am providing this stitched-together set of screenshots from that program:

I just upgraded the CPU on my friend's Dimension 5150 with success. I would like to replicate that on my 2400 - a much weaker machine. This computer is primarily used for casual internet browsing and occasionally watching a Youtube video. The only programs that really tax the CPU are my disk defragmentation and the program CCleaner. When I have a large internet browsing session of 100+ tabs, the CPU is also taxed at that time.
I would like to max out this computer using cheap upgrades parts I can buy on eBay. On my friend's 5150, I bought an upgrade CPU for $5 shipped and a thermal paste from ebay for 80 cents. I wouldn't mind buying a cheap video card and a CPU to upgrade this old workhorse