This may be off-topic here as it's asking for a software-recommendation. However if you've migrated from Windows 7, VeraCrypt may be an option and but if the PC is rather new (UEFI+GPT) this won't work. Personally I'd recommend BestCrypt as it looks like the best option to me (there's another tool by some German guys but it doesn't look better than BestCrypt and Schneier even "recommended" BestCrypt) —
SEJPM 18 hours ago