I would not rank McAfee very highly for ability to find malware. There are others better, plus an excellent help on this site
https://www.techspot.com/community/...lware-removal-preliminary-instructions.58138/
As to whether or not your symptoms really are due to a trojan, it is unclear at this stage. After scans following the guidance above, you will have a better idea, but it could equally well be something else, such as lack of full updates to Vista, or a bug in the sound driver.
Is the sound provided by a motherboard chip, or a separate sound card? In either case, you need to find out and obtain the latest driver, which will either be a motherboard driver or sound card driver. I do not take the repeated sound as totally significant, as you are doing things on the PC that make it give noises continuously, and the repeating noise symptom could simply be the Vista OS going into a loop.
As to system spec, just look in Control panel/system/hardware, device manager for basics, or google for Belarc advisor or Everest
http://www.softpedia.com/get/System/System-Info/Everest-Home-Edition.shtml You want everest home edition2.20 and be careful, it is one of those sites where it is easy to download something else by mistake, that you will be asked to pay for....
BTW, when you find the
application is locked up, you rarely need to emergency switch off the whole PC, and note this can be dangerous in various ways. It is almost always enough to press ctrl-alt-delete together (the three-finger-salute) and up pops windows task manager, wherupon you can choose the applications tab and stop the offending application in a controlled manner. But first, when you learn more, you will find the task manager a very useful aid to what is happenening. You can for instance, discover what thread is occupying all the CPU at the time. A controlled close also allows the application to write to standard error files, and sooner-or-later you will get one of us asking you to look for error in the event log - so there is lots to learn yet !