sudokusolver 0 Newbie Poster

help! i have a assembled pc with p-4 processor and 512 mb ram and 1.87 ghz with win xp sp2 installed.recently it crashed and i had to reinstall it again but now prob has appeared when i try 2 install or run a prog / app the application window appears annd works ok but suddenly it disappears and keeps running in background , when i try 2 terminate the prog using the task manager it 2 disappears !!! any idea on wats happenin 2 my sys??????