Take the lid of your PC and remove and re insert all the cards and memory. Twice.
Check for obvious crud/dust in the process.
Do the same for all the connectors going to the devices and the motherboard.
After 5 years, something is bound to have gathered a little crud.
I have done this on numerous PC's and at least half have gone on for a few more years, the others I threw away.
The other way to look at it is 'Wow that's a nice shiny new fast computer in the shop'!
After 5 years I usually update to something way better.
Cheers,
Damien.