Hidden, rescue, recovery, or whatever partition, which is loaded of your original OS shipped with your machine, is sometimes helpful to recover to factory default state. It might not be the best idea since your computer will be full of crap after, but sometimes if drivers are obsolete or time is all you need.
Here you go, this is what I have gathered so far:-
Thinkpad (Lenovo--Ideapad? I don't know) -- press F11 to access Rescue & Recovery partition Rescue & Recovery partition -- Windows PE 1.0 or 2.0 with some Lenovo stuffs, your machine detail + warranty status. Also including Opera which you can grab some info from internet via wired-network only. Sony (laptop & desktop) -- press F10 to access recovery partition--only system restore + full restore to factory default state. Note: it will quickly restore Windows image [5 mins for XP], but very slow to install apps + driver after getting into Windows [about more 35 mins] Asus -- press F9 HP -- press F10 Dell -- press Ctrl + F11 for Windows XP -- press F8 for Vista & hopefully newer; then click repair your computer and 'Dell Factory Image Restore' after logging in with administrator Fujitsu -- I still don't know what to do on XP though. However, Fujitsu adopt EFI very early, you may be able to click for menu at POST screen and get into Recovery tool/utility pretty easy. Otherwise, traditional ways are:- -- (Vista & newer) press F8 select 'repair your computer' Then go select restore to factory state. Sad thing is you need a recovery disc to execute the process--yeah kind of weird but Fujitsu recovery partition is only 1.5GB, that's why. Basically, it's stored diagnostic utility + erased hard drive tool + partition tool. Not really useful IMO.
Well I used to think of all this recovery partition that is a piece of junk, but after using it sometimes, it just comes in handy especially ancient machine which still works perfectly. Thus I think it would be a good idea to gather all this secret info in one place :-P After having enough, I will post again on myCapsules or 10ninox's blog.
Oh, one more thing, all this recovery partition is not involved with MBR. No matter how you did on your main partition, as long as you didn't hurt this hidden partition, it should work just fine. This is what I had a wrong thought.