I use Pretty Good Privacy (PGP). I just use the free part for the sensitive files on my hard disk. I don't need the pay-for-it part that does email and whatnot.

PGP will encrypt a file or a directory of files, much like WinZip.

I am religious about keeping my financials encrypted. Glad of it when my hard disk died. Took it to a shop where they recovered the files. Since the shop couldn't decrypt them my info wasn't compromised.

Don't think about using crypto to hide illegal stuff. The 3-letter agencies have their ways.