Originally Posted by RainDawg

Use Quickpar...it's the most comprehensive filechecker of it's type, and is free software:
http://www.quickpar.org.uk/

I personally use as close to 20% rendundancy as I can. As you add files, it automatically sets the block size to be the most efficient that it can, generally > 95%. I also recommend unchecking the option that forces blocks to be the right size for usenet posting, unless you're planning on seeding them there.

I am currently going through my collection of 180 DVDRs and checking them for errors, and reburning as much as possible to new discs, with par2 recovery volumes.