As an end-user excluding actual real vendor problems, must address any OS, drivers, updates, etc. new installs and the like before blaming the vendor. Your post makes no mention other than buying new another system to resolve your problem(s). You should be aware of defragging, cleaning old installs after removal, spyware/malware issues, any Kazza type file sharing enviroments, etc. plus start-up loading pgms,. robbing resources. In other words, get your "system in order" to attempt intense tasks. Gaming and/or multi-media based system will demand alot from the system and the less overhead it has to deal with the better the results. On top of all this, having a well cooled and stable power source is an "absolute must". Looking into better power beyond what was offered is defenitely a plus. Cooling issues address many later problems due to failed fans or yet more h/w installs(stuffed system) can create havoc under "heat duress", so expect sooner or later flaky problems to arise. OEM based system tend to offer "a system/model" and later additions will likely start the downgrade process with current installed p/s unit, they don't offer much room to grow on. I hope this helps...
good luck
-----Willy