on my desktop computer (version xp pro). currently i am on my laptop now and figured out that my desktop has the Issas.exe virus/trojan worm. i removed one infected file and computer shop removed the other. i continued working on it myself and tried some registry changes and now it is bluescreen. the error message pop up appears "Isass.exe at top; "Endpoint format is invalid". i am able to select safe mode but not get onto desktop much less my control panel. the error message box still appears. it is an old system but i have to fix it until i can afford to buy new computer. please help.