Powers up to White screen, attempts to load twice, then shuts down?

been busy.... done that... re-installed os, was working fine then repeated problem... done disk repair got the following...thru verbose..

iMac7,1 2007 SnowLeopard

Ran sudo /sbin/fsck -yf

acme back...

invalid key length

(4. 1882)

the volume MacHD could not be verified completely.

/dev/rddisk0s2 (hfs) EXITED WITH SIGNAL 8

Your hard drive has completely failed. Replace it. Here's how to do it: iMac Intel 20" EMC 2133 and 2210 Hard Drive Replacement

Appreciate all assistance Mayer... have overcome previous difficulties and have the Mac back in action working well so far... it turned out that my original difficulty arose (these are my now educated opinions) when my Mac was attempting a 'faulty' firmware upgrade {I know this because I had restored my Mac 3 days ago and was working fine then I did an update and was thrown back to boot up difficulty and as described by my previous comment} resolved this with a 'virgin install' from disc...so now at the mo I will keep original firmware updates going and keep you posted periodically etc.

Now taking all that into consideration I would like to give a tit-bit of diagnostic of my original [problem] the non-functioning mouse/keyboard... many other user found similar difficulties with this (not just on this website but on the wider Mac fraternity) and after the usual recommendations fail to resolve the issue the popular advice was to take it in for [an expensive] Mac repair... MY ADVICE WOULD BE TO CHECK THOROUGHLY 'STICKY BUTTON' in other words make sure there are no keyboard keys in a depressed state as was on mine!!! this was compounding my frustrations initially... so a word of advice Mayer would be to include this as a part of user check list when encountering a Mac firmware/boot up issue.

Again I would like to thank you for you're support, it was reassuring and extremely important knowing I had a place to turn... who wasn't 'holding out their hand for 'payment first'... I think more companies and websites should remember that users are people and not all people have a job or disposable income to fritter....

Yours appreciatively,

John

John, probably 95% of the answers on iFixit are given by volunteers, not iFixit employees. Although I'm not completely uncompensated (I was given a tee shirt by iFixit about a year ago). I would think a sticking key would be something that would be noticed pretty quickly. If I were you, I'd still do a "write zeros" option reformat of your hard drive to eliminate any bad blocks and then do a re-install of the system.