Looking for a cheap acceptable graphics card for an old PC

About 4 years ago I bought a $75 PC at a garage sale. It was weak in the graphics area (integrated) so I put in a GeForce 6200. It was better, but was still week; youtube videos stutter and sometimes only play about 1 frame a second. Lately the screen has been going black and it messages "The display driver has stopped responding and has recovered." (The drivers are up to date and indicate that they are working fine.) The only change recently has been a switch from a 10 foot DVI monitor cable to a 15 foot DVI monitor cable (could this be the problem?) In the Windows Experience scale the PC score in the 4's, but the display graphics is a 2.2.

Anyway, what cheap/on sale ($20-$50) video card(s) provide enough bang for the buck to get an older moderate PC up to speed enough to play video? (And considerably better performance than a 2007 GeForce 6200)