Avoid system-formats to save your PC! Please Backup!

I've seen a lot of my friends saying that they had to format they're computers (and thus lose important data) because some virus/trojan had infected their PC. They say they need to re-install the OS altogether to fix the problem and there wasn't any solution.
However, more often than not this isn't true. Windows itself provides several ways to fix the mistakes you made or get your pc back to an earlier normal state.
If you happened to try to edit some important Windows files (intentionally or unintentionally via some program) and screwed your system up causing it to not boot or pop up several message boxes talking about errors, well then a system-format isn't the only solution.
There are simple ways you can fix this without losing out on important data!
You can just use a Windows Component called System Restore to restore your computer to an earlier date, when your system was stable. You can even try reverting your registry to an earlier state if registry-editing has caused you problems. Or there also are other backup programs like Norton Ghost that restore your windows files to a predefined stable state.
I'll explain these backup methods right away.

Backing up Registry.
I've already mentioned in the article before this one how to backup and restore your registry.
This is especially useful when you've edited values in your system registry and it has caused your PC to become unstable.
Check the article out here.

Using System-Restore.
This could well be one of the easiest and quickest ways to get yourself out of a mess you just got into.
What system-restore does is, it restores your computer to an earlier predefined date, just like taking your PC back in time, sometime when your PC was stable.
All you've got to do is regulary set system checkpoints whenever your system is stable so that you can effectively restore to those points in times of trouble!
Using System Restore won't affect newly created or deleted files. It only reverts back to a previous system state wherein it will disregard any newly installed software or application.
Anyway, lets get down to business on how to make a Checkpoint.
Click Start>Programs>Accessories>System tools>System Restore.
Check the "Create a Restore point" radio button and click Next.
Here, give your restore point a suitable name. If your doing this after a fresh install of your OS, name it something like "Fresh OS install"!
Then click Create!
Your done! Your system restore point is created! :)

Now to restore your computer to an earlier date, follow the following steps.
Again navigate to Start>Programs>Accessories>System tools>System Restore.
This time choose "Restore my computer to an earlier time"
A calendar will then be displayed featuring all the system restore points that are available to you.
Note that, windows creates system restore points on it's own whenever certain programs are installed and you can choose to restore to these points as well.
Anyway, navigate to the date you created your desired restore point and on the right window you will see a list of restore points that were created on the day.
Choose the appropriate one and then click Next.

Here you've got to confirm your restore by clicking Next again.
On clicking next, your pc reboots and the system-restore process initiates itself.
However, a system-restore isn't always successful. If the restore is unsuccessful try another restore point.
Remember, the best way to keep your pc and your documents safe is by regulary making restore points. The more the better.

Using Norton Ghost.
Norton Ghost is another wonderful software that quite literally saves your ass when Windows Components/files get corrupted and even System-restore doesn't work.
What it basically does is that it creates a virtual image of your disk and saves it another disk on your computer. So when the disk gets corrupted, all you've got to do is replace the corrupted disc with the content from the virtual image! :)
You can simply create an image of your C: or wherever your OS is installed and then in times of trouble, just replace the entire C: with an earlier, stable state of the drive.
I'll provide links here to some wonderful tutorials/guides made on using Norton Ghost.
Creating Images: http://www.symantec.com/techsupp/tutorial/nghost_10/2005100407425562.htm
Restoring from images: http://ghost.radified.com/ghost_3.htm

Other backup.
Well for frequent bookmarkers like me, it's disastrous when I lose all my Mozilla Firefox bookmarks after a format or unprecedented error.
What I do is, I use MozBackup! :)
It's a simple freeware utility that allows to create and restore backups for your browser.
It's a tiny 1mb file. You can download it from here.

Apart from these backup methods, you should also always backup important files on a drive apart from where your OS is installed i.e. usually C:.
Better yet, if you've got more than one HDD, save a copy on the other one or even on a USB stick if needed.

Remember, formatting isn't always the solution. Even try google if its a specific application-related problem your facing. You could save yourself the trouble of losing out on important data!
Keep backing up! Ciao! :)