geforce GT 520 Zotac cant do 1080p

Oh OK, I thought you said Task Manager....

 

Not really my area of expertise, but it's probably your old A64 single core cpu. Too old man, not enough for HD. Dont know if you can decode 1080p purely on the card tbh

 

Your CPU is slow, but you're right, the video card should be decoding AND rendering the 1080p video in hardware on youtube.

One thing I noticed on an old P4 3+ Ghz I have running a PCI nVidia 8400GS (same as a GeForce 210) is that it only decodes and renders via GPU when playing back full screen. Have you tried that?

If you right-click the youtube video and bring up the drop down menu, it should have an option "stats for nerds" and it'll show you if its rendering and decoding via software or hardware.

Make sure you have the latest version of flash installed.

Linux is terrible with flash accelerated playback by the way. The drivers crash and/or you get strange green tinted video. Win XP is much better for this.