There is really no general procedure to checkout your system. You can run sfc /scannnow
in elevated cmd to see whether you have corrupted system files. But that's about it. If a specific program like your guitar program has problems, you'll have to sort them out on a per case basis.
As far as running programs eating your CPU - disable everything except the AV program in the startups. WinPatrol
is an easy tool for that - unless you want to use msconfig. Else, close programs when they are not needed.