[Clueless101]

Everytime i try to open any programs other than those on the right hand side of the toolbar at the bottom of the screen (where the clock is), i get an error message saying that the DEP (data execution prevention) has closed the program down and when i close that message, i get another one asking me if i want to send an error report. when the DEP message comes up the only optins are to close or 'what should i do'. the what should i do option shows me how to deactivate DEP going through start, help and support... and so on. But i cant do this because when i click on help and support, the DEP kicks in and doesnt alow me to open that. Do i have a virus or is my pc just malfunctioning? im running on windows xp profesional (sp2) and when i do a virus scan it does come up with a Java/Exploit.Bytverify trojan which i cannot seem to remove. i have had this problem for around 4 - 5 days now and at one point it did seem to have sorted itself out as the pc worked normaly for 36 hours. On one occasion another error message came up which refused to go away for good. when ever i closed it by clicking the x, it came back along with a DEP message within 2 - 3 seconds. the error message was as followed:

Explorer.Exe - Application Error
The instruction at Oxfe9ed475 referenced memory at Oxfe9ed475. This memory could not be writen.