This should definitely be investigated before investing time getting an alternative OS up and running, along with the troubleshooting and training that comes with it.

Upgrade to the latest CPU for the platform. For $25 you could gain an extra 1+ Ghz or more cores.

Max out ram, for DDR2 systems this is usually 4GB - 8GB. 2GB sticks can easily be had for under $10 a stick.

Replace hard drive with SSD. Especially if it's a low RPM hard drive. 128GB SSDs can be had for $35 on sale.

The above upgrades will easily boost performance whatever OS is already running on the hardware, and total time to install should be 1 - 2 hours.