Back everything up and get a new disk ASAP and do a clone which will then allow you to run everything as before. even if teh old disk is not a problem you will have peace of mind.
Run a decent Virus Scan - or several from different sources. Run a Malware scan - Malware Bytes, it may pick up malware missed by the VirusScan.
Have you installed anything new recently - if so, use System restore to before then, or if nothing new a system restore to a day or two before the problem.
Run a defrag.
When Chkdsk is running does it find any bad sectors and are they marked?
At 7 years old, it still has a few to go ... I had a Win 98 based Dell and I finally decommissioned it in 2009 - over 10 years running 24h/day for most of that time.
M H C
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