SERIOUS security problem..Please assist me

Previously i had reported of my laptop being used by a unknown person , resulting in various suspicious activities in my laptop. And as adviced by seven forum experts i did a format and reinstall the window again

But again my laptop is poping up unknown messages( attachment added) , and mouse cursor still moves resulting inthe mouse pad getting blocked and sometimes laptop freezes with a strange sound..

i tried to contact my antivirus support centre but till now no any help from them.

i am expecting a help u people out here. please help me and tell me whether i can get rid of this hacker if i change my HDD or modem as nothing seem to work. ?? please guys

If you use a wireless router you may have someone close by tapping your signal. Change all your passwords and use wpa/wpa2 security. What type of connection do you have?

Golden : I was doing nothing. the laptop was in still mode.

madcratebuilder : I don't use a wireless router. i use usb modem or somtimes mobile tethering.

bobafetthotmail : i very rarely use internet explorer. and i use mozilla firefox up to date version. i never gt any such pop ups before.. and mouse cursor moves means, whenever the laptop is in still mode , the cursor moves of its own wthout touching the mouse. after that the mouse pad gets blocked , means it doesnt not work. it happens only when connected to the internet

mitchell65 : After clean reinstall it worked fine, but after few days again the problem started..

@Everyone, guys will changing the HDD or modem( internet connection provider) help me to get rid of this virus or hacker. because nothing seems effective against it. neither antivirus nor clean reinstall. After i posted this thread tday afternoon, the computer got freezed with a strange sound and i had to swith it off through main switch