If you can, try to start backing up your files.
Warning: Backing up your files doesn't give you any more peace of mind. Infact, it makes you more paranoid, but it's probably a good idea anyway.
If its important stuff, make sure your backup drive is a mirrored RAID System with at least 2 Disks (NAS, A Dual-drive USB Disk, or a server you know has mirrored drives), or backup your backup regularly.
This now comes from someone which lost valuable data multiple times because of faulty disks or because upgrading CPU and GPU was seemingly not done properly. Disks do not fail too often. But more often than not, you tend to overlook the signs of an imminent disk failure (growing SMART errors, Files getting corrupted) and wait too long before it blows up.
Maybe this has made me paranoid.... still, RAID 1 sounds like a good idea to me almost everywhere
Oh, and having a separate Data partition on a separate disk is a good idea anyway as dragonsoulj writes... did that because I wanted to use an SSD as System Disk, turns out it had a much more important upside than just preventing your SSD from going bad too fast when my SSD finally got "bad"... it did not really blow up, but it got filled to the point where windows could not start anymore. Had to yank in a new drive just to reinstall windows. Thanks to the separate data disk, all my data was still there, I just had to reinstall all my programs. I could then go on and wipe the filled SSD for later re-use.
Apart from my many Hardware related troubles (that I most of the times was to blame for), I never had any problems with Windows 7, so I really cannot help on that topic. Win7 has been stable for me for 4 years, so I am not looking forward to the day when I will finally have to make the switch to a newer Windows version (hopefully not Windows 8 anymore by then)
It's important to make note that RAID is more for fault tolerance than backup. You can still get that virus which encrypts all your important files. RAID doesn't help you there. You can also have a physical catastrophe, where your geographic location suffers a flood, fire, or theft. RAID won't help there either. The best way to back up files is to copy them to a removable hard drive and then move those files offsite (like from your office to your home, or some trusted secure location). If you're worried about data theft, encrypt your backups (and don't lose the encryption key! Windows encryption uses the SID, which gets cycled on a new install.. which means total data loss!). It's also a good practice to back up to more than one drive. If your backup drive goes bad, you still have recovery capabilities.
In terms of backup frequency, you really just have to ask the following question: How much work can I afford to redo in the event of catastrophic failure? Some people can go back a week, some a day, some an hour, some 5 minutes. In my case, I vary between 4 hours to a day between backups. Also, you don't want to just overwrite your previous backup. You want to make a sequential backup, so if you need to make a recovery, you have the option to go back to any point in time. I go with 5 full backups with a 1 day interval, 4 full weekly backups, 6 full backups on a monthly interval, and 1 full yearly backup. Each backup is on a cycle where the oldest one gets replaced or archived. Why do this? Suppose you have some sort of malicious agent which slowly adds corruption into your data. You don't discover it for a month. If you only cycled between 2 daily backups, you also backed up the corruption and lost an unknown amount of data and can't trust the integrity of your existing data. It's not as bad as complete data loss, but it's still pretty bad.
Lastly, it's also a very good practice to go through a restore process in order to verify the integrity of your backups and backup process. Especially in enterprise cases where the backup process is complicated/esoteric. There are some nightmare stories about a flawed backup process which only got discovered when data loss occurred and needed to be recovered, only to find that the tapes for the last three years were blank.
Coincidentally, I actually had a hard drive failure last week and had to completely replace it. Fortunately, I had very recent back ups, so the only time I lost was the time it took to purchase a replacement and re-install all of my software tools. Zero data loss! Oh yeah!!!!
In my opinion, the #1 responsibility of a sys admin is to keep good backups. If they don't know their backup process, know where the backups are, and know that they're good, it's a dereliction of duty and should result in immediate corrective action, up to immediate termination of employment. Everything else is secondary. If you do it yourself, make sure it gets done. Your progress is only as good as your last backup.