Issuess...again

here is the thing....i have ATI Radeon HD 2600 Pro AGP 512 mb,1.5 gb of fully working ram (tested),60GB maxtor HDD also fully tested,my errors occure when i go to play league of legends.i can play call of duty 2 for hours (botj sinlge and multi player) without a single crash or restart but after like 3-6 minutes of legeue of legends it crashes and its my favourite game so please help me.the errors i get are all BSOD and they all indicate DRIVER_IRQL_NOT_LESS_OR_EQUAL so its my graphics card right??please give me working ati driver please....im desperate.dont point me to sites because after downloading approptiate driver for my card from ati in the installation it shows nowhere ATI display (in catalyst installer) so i have to go to update it manually and this is what happens since i did that.please help me i appreciate even readin so thanks