In order to assist you better it would be great if you could help us with these items
Currently does the machine have McAfee installed on it?
What is the operating system on the machine?
What is the error message when you attempt to go online?
Also how are you attempting to go online? ( Aol , Mozilla firefox or Internet explorer etc...)
If McAfee is installed . i would suggest that you right click on the M icon on the lower right hand corner of the screen and select a scan ( full scan) and allow it to run detect and remove anything it finds. ( note down the detection name if possible)
Once done.. let us know the status and error message when you try to go online ( if you have means to post on the forums from say another machine etc..)