Cannot dissconect my net after 30 minutes

Dear friends,
My computer connects to the internet normally.After 30 minutes , suddenly the computer adjusts itself for the best performance (in visual effects) and back to normal.Then i cannot disconnect my net.It also displays WIN 32 Application error.Is it Virus?pl z help...sir. I Have followed the 8 steps in the above main thread and have attached the log files.Please help sir....Do reply..
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