It sounds like it served you well and it's hard to guess why your preferences vanished but it's not unheard of.
Sadly I can't find the Lion version of this link -> http://support.apple.com/kb/ph10941
If you wish to continue with this OS it's time to find out where the prefs are and when you get back to where you want to be, backup your prefs.
I own a great 7 year-old MacBook Pro, still running OS X 4.11. Before you laugh at me for not upgrading it has worked like a dream and never felt the need to upgrade though am sure I'm missing some good things by not doing so.
Anyhow the other day, down to about my last 6 GB on my internal hard drive (87GB used of 93GB), my Mac Mail started misbehaving and asked me to restart.
On restart, my whole desktop, icons/thumbnails etc were all jumbled beyond recognition, sidebar was almost empty, Mac Mail when opened asked me to start from the beginning (i.e.set up an email account etc etc). I did this, because I could remember the settings for my addresses. Then Mail asked me to import my old mailboxes, which it did - but everything looks different, fonts, no signatures (they'd taken ages to organise) and no inbox or sent meail folders.
Ditto Firefox and Safari - when opened, all bookmarks have disappeared, and all autocomplete passwords for sites have gone.
It's clear my system is pretty messed up. Luckily, I have a bootable Carbon Copy Cloned external drive of how my Mac used to be 6 weeks ago. When I used this to boot, everything above was back to normal.
My questions are:
1) Is there any way to get back to where my system was before the blowout using my Cloned Drive? I.E. Can I simply erase the contents of the internal drive and 'paste' over it with the Cloned Drive? Is this risky?
2) Is there a less invasive way - is it easy to reintroduce the old preferences from the Cloned drive?
3) Do I need a new hard drive?
Any help would be much appreciated.
Model Name: MacBook Pro 17"
Model Identifier: MacBookPro2,1
Processor Name: Intel Core 2 Duo
Processor Speed: 2.33 GHz
Number Of Processors: 1
Total Number Of Cores: 2
L2 Cache (per processor): 4 MB
Memory: 2 GB
Bus Speed: 667 MHz
Boot ROM Version: MBP21.00A5.B08
MacBook Pro 17", Mac OS X (10.4.11), Intel Core 2 Duo