Your motherboard supports Intel® Core™2 Quad Processors (
https://www.biostar.com.tw/app/en/mb/in ... cpusupport).
This means that for a very low cost you could upgrade your cpu to something that is still not very energy efficient, but anyway more than decent for Folding@Home or Boinc.
If you look on Ebay, you could find a lot of Xeon processors compatible with your motherboard. Your socket is 775 while Xeon's socket is 771. These two sockets are compatible with an easy modification of the motherboard (you just have to cut a tiny piece of plastic with a knife). By upgrading to Xeon Quad Core you could get a good quad core system with less than 20$.
For example, my computer (Abit IP35-V motherboard) had a shitty Celeron E1200 (similar to yours)... With 20€ I put a Xeon L5420 on it.
Xeon L5420 is built on 45nm, it's 2.5gHZ Quad Core and has a TDP of only 50W. If you are lucky and get a L5450 for a low cost, then you would have 3gHZ Quad Core with the same 50W TDP. Definitely a good and cheap system for distributed computing.
If you do not want to modify the motherboard (I assure you, it's very very easy) you could look for 775 quad core processors, such as Q9400, even if they are built on 65nm and consume 65W)
I drive a Nvidia 750Ti with no bottleneck of any sort with a single core of my L5420. Probably you could use a 1650 without any issue, but I cannot assure you about it.
Then, of course, if you spend 400$ for a Ryzen system you will double the performance with the same energy consumption... But not anyone has 400$ to spend for volounteer computing.