Time finally has degraded my psu? gpu failure...

hello everyone.
so i have this second pc that i use mainly for web serfing, watching tv and word processing.
its almost 7 years old hp.
it has
AMD athlon xp 3200+
some hp mobo.
2X 512MB sd ram 333mhz
1 WB 60GB drive
1 CD ROM
evga fx5200 128mb
http://www.newegg.com/Product/Product.aspx?Item=N82E168... tv tuner
250W psu. i believe its from DELTA. seems its in mid and high quality. and feels heavy and solid.

i have pretty good knowlegde about computers, i fix, build, overclock computers..
so
i have this fx 5200 connected to my 17 lcd and Tv (by s video)
it was totally fine until today, when i opened up a video file, monitor blinked once per second. from sleep mode to on mode. but screen was frozen. i was actually hearing the sound of the video, but with frozen and blinking screen.
after restarting several times, im now seeing black , white, lines all over the screen sometimes, and whole pc locks up. some times it just blinks, sometimes it locks up like that.
this gpu is fanless one but i have one 80mm attached to the heatsink.
first i thought it was gpu dying. but the 7 year old psu caught my attention. so i took out Tv tuner card, and it was still doing it.
now i took out the gpu and connected my monitor to mobo integrated gpu.
it works totally fine.

what could be the cause of this??
for now im thinking the gpu is going bad...

if its the gpu, should i get a used AGP card. or its just better to build a basic pc under 250$?
this old pc consumes lots of power and it cannot play youtue 720p videos without lagging.