One would be surprised at the amount of trash accumulating unknowingly on your pc. I use Norton 360 which has a function to run a custom scan and delete temp files and histories. About every other day I run the scan to clear the the trash. I just cleared 6,940 IE temp files of 178 mb plus a few other temp files. 5,000 to 7,000 IE files are common. There is a function in IE tools--safety whereby it can be set to automatically delete the files at each exit. May be worth checking into if your pc is running slowly.
IE temp files
Just remember that after you delete them, they're in the recycle bin, which must then be emptied. This leaves big "holes" in the data on the hard drive, leading quickly to fragmentation. It's good practice to defrag the drive immediately after dumping temps and emptying the recycle bin.
A search can also be run using *.temp,*.tmp,*.chk,~*.* ;as Oldgardenrose stated, you'd be surprised at the amount of junk your PC generates.