NOD32 vs BitDefender

yes, it is unusual for sure, but if you are sure that it is conflicting with something, remove it for sure and give a few other av's a try.

 

Which process was using 15 % all the time? If you can remember it. This are all bitdefender related processes: bdagent.exe,bdmcon.exe,bdss.exe,livesrv.exe and xcommsvr.exe Do you have Spy sweeper installed? That could cause problems with most other security programs BD hasn't any problems.
Other antiviruses use sometimes also more then 15 % or 1 % especially when they are checking your hard disc.

 

When You turned off some services did You turned off Terminal Services service, if You did set it on Manual or Automatic and everything should be fine. If this service is turned off than Bdss.exe process will use CPU for about 15%.

 

Terminal services is shut off.

 

Set it on Manual or Automatic and see if Bdss.exe now is using 15% CPU. Just do that when You have time and let us know the results.

Best Regards