if anyone could help i would be greatful as this has irritated me for about 6 months now..

when i play a video that has 720P its just choppy freezes while audio continues etc just a mess.. but i can play HD videos just fine for example

Breaking.Bad.Season.1.720p.BRRip.XviD.AC3-FLAWL3SS PLAYS CHOPPY AND SCREWED

Entourage.S08E01.HDTV.XviD-ASAP PLAYS JUST FINE

WWE.Money.In.The.Bank.2011.07.17.HDTV-TT JUST FINE

im running windows 7 pro
2GB ram
www.newegg.com/Product/Product.aspx?Item=N82E16814161347

(HIS H435H512PH Radeon HD 4350 Silence 512MB 64-bit DDR2 PCI Low Profile Video Card)

as my video card

please any help would be great i play files using VLC and media player classic