Some payback calculations assume x rate of return as a comparison, others don't. Don't assume.

Also, remember that the life of solar is greater than 7 years, so after that it's all "gravy"...or, in other words, you get a dividend into perpetuity (or when you sell the house.) Because the payback time is less than 10 years, you know that the dividend is better than 10 percent/year, which is far more than one can expect from stocks. So, if necessary, you can extend the payback time a few years to account for a regular rate of return, but it still ends up positive.

Also, they are in inflation-proof investment, which is better than can be said for almost everything else right now.

-Daniel

I admit it, I blew it on the journalling point. And you're right on the money about defragmenting. Here's a point another poster made to me: if your drives are IDE and not SATA, the journalling in NTFS might not always recover after a crash, which explains what happened to the PCs in my office (corrupted registries, etc). That's interesting, isn't it? That the drive type might affect the outcome?

I learn something every day here.