I have a mid-2007 iMac (specs in sig), so the computer is about ~5 years old. It's treated me great for many years, but about six months ago, I ran into some problems. Flash videos were pretty darn laggy and would lock-up my whole computer for a couple seconds at a time; applications were taking longer to open, the system as a whole felt sluggish, and boots were taking 2-3 minutes versus ~30 seconds like they should. I went to repair permissions, and there were hundreds of permissions problems. I then went to repair the disk, and it told me that the operation couldn't be continued due to an "invalid node structure." So, I decided to completely wipe the drive and do a fresh install. That seemed to Band-Aid the problem. It still didn't feel near as snappy as it should; but the computer was at least usable. Tonight though, a storm knocked out our power. Upon re-booting my iMac, the boot took a good 7+ minutes :-/ Once again, everything is sloooooow. And again, all my permissions were f-ed, and it seems I once again have an "invalid node structure." *** So, my questions: 1) What exactly *IS* an invalid node structure? 2) Is it safe to assume this HDD is pretty much ****ed? Or might there be something else I'm missing? 3) And lastly - and this is more subjective - what do you guys think of putting a ~120GB SSD in the iMac, instead? I don't have much disposable cash. But, I need this computer to work so I'm gonna have to fix it. And I'm looking at my free space; and on my current drive, after 4+ years, I've only used ~80gigs. All my media and stuff is on my PC, and all my Adobe projects are on an external. Plus I have lots of space on my NAS. Considering a 120GB SSD is about the same price as a 500GB HDD right now, I'm kind of thinking of just going with the smaller, but much faster, storage. Am I crazy?