Dell Vostro 430 Graphics card query

Hi there I was wondering if someone could advise on a part upgrade. I am currently using a dell vostro 430, so it's an older machine (2009) but which has been perfect for my needs to date which is making music using ableton and some graphic design, nothing major so no gaming or anything like that. Only problem I have with it is that it is currently running Windows 7. I recently tried to upgrade to windows 10 as none of the new music plugins coming out support windows 7. After updating bios, drivers etc I upgraded to windows 10 but the graphics were awful, really blocky like they were straight out of a zx spectrum so I put it back to windows 7 for the time being where there are no such issues. As far as I could see I had the most up to date driver for the graphics card in the machine which is an NVIDIA GeForce 310.

I presume that I need to update my graphics card but I'm not 100% sure what I should be ordering. Since I bought the computer I have upgraded the memory and installed a 500gb SSD. Everything else is original. Current computer specs are Intel Core i7 860, 2.8 ghz, 16gb ram, 64 bit. Monitor is a Benq G2420. As far as I'm aware the power supply is the original that it was shipped with which is a 350w. I have the service tag and had a quick look on the dell site but couldn't locate the power supply info on the specs for my computer.

I was wondering if someone could recommend what I would likely need to be able to get sharp graphics with Windows 10 that would work with this machine. Preferably it would need to be under £100 as over that it's getting into the territory where it might be more sensible to replace the machine with a more recent one but if needs be I might be able to squeeze a little more.

Cheers John Hutchison