The other day I cleaning up my laptop when I came upon some photos that I had long ago given up hope of ever finding---some of these I posted on this site. It just goes to show that finding stuff on a cluttered hard disk ain't easy.
Not just for you, mind you, but for the computer, too. Which explains why overstuffed computers are slow in booting, slow in launching applications, slow in retrieving files, and slow in just about every other computing function.
So go ahead and get rid of those files that you've kept all these years "just in case." Your hard disks need defragmenting now and again so your computer can access files faster.
Remember, when saving files, computers will in general just throw bits and pieces all over the place. All it keeps are the "addresses" of where these bits are kept. So the closer together these bits are, which is what defragmentation does, the faster it is for the computer to gather and give you the file you've requested.
Your registry also needs dusting once in a while.
For you to do an even better spring cleaning, you can use freely downloadable utilities such as EasyCleaner (http://personal.inet.fi/business/toniarts/ecleane.htm).