Should we trust our local hard driver? Are we confidence to keep our data on our local hard driver without a backup? NO, I would say we should never ever do this. It is too dangerous relying on the reliability of your HD without backing up your data even you have RAID configured in your computer. It is just not a good thing to do.
One of my colleagues was working on his laptop the other day. All of sudden, he called me to come to his desk to check what this noisy sound came from. I went to his desk, and immediately pointed out the HD in his laptop is dying because that sound is typically a sign indicating that there is something wrong inside the HD. I said I can try to recover some data but no guaranty. He was very depressed at that time becuase it would lose his 2-year class notes. He was lucky as I successfully recovered data before the HD completely dead. This is just one of the cases. How many times did it happen to me? At least 6 times this year so far. I think this number is not low because I am not working on a computer hardware shop at all.
I agree that backing up your local data is not a easy step to accomplish if you don't have the right tool. But these 2 free tools make me feel so easy to do this kind of boring but important job by just couple of clicks. Check it out and back up your data right now.
SyncToy V1.0 for Windows XP from Microsoft
Allway Sync - file synchronizeer that works