I have a Compaq Presario Laptop 1600i. It has a 300mhz CPU and 192mb of RAM. It was originally delivered with Windows 98. I successfully upgraded the op sys to Windows XP, SP2 and installed a larger 20GB HDD. The laptop is in excellent shape with 2 good li-ion batteries, AC and DC chargers and a desktop docking station. My question: Can the motherboard be upgraded? How much would a new mobo cost, where would I get it and could a diyer do it himself? Thanks for your advice.

No, a motherboard cannot be upgraded due the way a laptop is constructed. At least, not without considerable effort.

Even if you could find a better motherboard that would fit in the same form and thermal envelope, it would probably cost more than a new laptop unless you bought it in lots of 1000.

Most laptops are designed around the main board, the only one that would fit would be one from that series, and we are talking four hours time from an experienced laptop tech.

The shop where I work charges 115 per hour for laptop work (clean booth only)

you would need New mainboard 200.00
New CPU 150.00
New RAM 120.00
labor 460.00

These are estimates for parts, not labor.

Not cost effective.

cpu replacement is possible, but still takes four hours.

I don't want to question you oldf@rt, but I upgraded a laptops processor before and it took about 15 minutes, counting opening and closing it.

No worries, I have seen a couple that took only a few minutes, the laptops had a special access underneath the keyboard. These took about 45 minutes. Most are blocked by the heatsink and fan combo, which can only be removed by disassembling everything else. Plus working from the clean booth adds time.