Securely erasing data

Hello all. I'm in the process of wiping my hard drive and reinstalling everything. I'm doing a 7-pass erase on my 320GB WD external hard drive that I was using for time machine back up. Once that is done, I'm going to 7-pass erase the free space on my hard drive and then back up my current hard drive to the WD external and then 35-pass erase my Macbook's 160GB hard drive and then restore it from the back up. This should make everything but the data that I backed up to the WD after the two 7 pass erases recoverable, correct?

Wow, you must have a few free weeks to do this.

Really, zeroing out the drive is all that's required. Nobody's short of the CIA are going to be able to resurrect anything from that. Drivesavers (the best in the biz) don't even bother trying to recover from zero'd Mac drives anymore -- too much work, not enough results.

Unless your drives are stuffed with state secrets or child porn, I think the multi-pass is ridiculous overkill. The only reason Apple put those option in in the first place was to win some government contracts.