I'd be concerned about possible hardware failure if you were getting major file corruption problems - though it's always possible that they were related to some kind of software issues (possibly a virus, or buggy drivers).
There is a utility to repair damaged PST files called scanpst - it should be somewhere on your Office our Outlook CD-ROM. However, if the file is very corrupt, I suspect you won't be able to get it back that way. :sad:
I'm lucky - I have the hardware and software to run daily unattended backups (weekly full and daily differential) to a large hard disc dedicated to backups and scratch space. The backups are then automatically verified, copied to DDS-4 tape, and the tape copy verified. The system emails me to confirm that both the backup to disk and the copy to tape have succeeded.
The same system allows me to 'disaster recover' in a few hours - though I don't have the full-blown Disaster Recovery module. All I have to do is reinstall Windows and install the Windows service pack I was on. It's not necessary to install all the latest drivers, hotfixes and so on - they'll all be recovered from the backup. From there, you install the backup software (evaluation mode is fine - so you don't need to find the product key), catalog and inventory the tapes (in my case just the most recent two, assuming they're intact), then tell it to restore the latest full and any subsequent partial backups. It figures out precisely what needs to be restored, then sits there and asks for the tapes as it needs them. If the backup hard disc is intact, it's even easier and faster than bothering with tapes. After the restore is complete, a single reboot and my system is back. It saved me a year ago when the computer crashed and my C: drive finished up utterly corrupt (quite what happened, I don't know - NTFS is normally pretty robust). I hadn't the time to sit down and spend several days reinstalling, especially as I was only months away from a new main computer anyway.
Of course, you easily retrieve single files or folders from this setup - if they're still in one of the backups on the hard disk, it takes literally seconds to restore.
However, the hardware, software and media involved in this level of backup is far from cheap (around 1000 pounds in the UK at current prices - maybe a little more, and you do need a SCSI controller and cable for the tape hardware, so they're extra if you don't already have them). The only thing I don't have is a data-rated fire safe for the tapes. Really, this is a business level backup system.
These days, you can get a worthwhile backup system with reasonable capacity for a tenth of my kind of system, because of the current low price of DVD writers. Four and a bit gigabytes won't back up more than the simplest modern computer in its entirety - but gives you loads of space for backing up your important data.
Nero 6 has a "Back It Up" utility that might help; it's a shame that it uses the built-in scheduler on Windows 2000 and XP, so it won't run when logged off, but it's still a start. If you've got Nero 6, you already have the software. Even if this software doesn't allow you to recover your Windows installation (I don't believe it does, but I haven't fully investigated what it can do), it is your data that's most important.
A decent DVD writer (NEC ND-2500A is what I have - an excellent drive for the money) and say ten 4x DVD+RW discs of a decent brand should get you going - the total outlay for those items in the UK at the moment would be around 110 pounds - and of course, you then have a DVD writer for other uses. Indeed, if you only have a few hundred megabytes you really need to protect, a CD-RW drive is good enough at least to get going with.
The important thing with backup is that it has to be easy - at worst, load a disc or tape and start a program every week - otherwise it won't get done. I used to have a backup system that required starting manually, and I was very intermittent in backing up.