Can I trust Windows 7 System restore?

Ok so basically i wanted to get themes for my windows 7, So i had to play around with the explorer.exe, ExplorerFrame.exe OobeFldr.dll and shell32.dll located at the sytem32 folder, While doing this I renamed the shell32.dll and tried to transfer the new one for the theme. Unfortunately it did not transfer no matter how much i tried.It owuld appear like it was tranferring but I coudnt find it in the system32 folder, all i could find was my renamed shell32.dll file. So, I decided to restart my computer, and when i did, it told me that i am missing a shell32.dll file and i cant run my desktop, i was stuck at the home screen where you type your password. I tried running at safe mode but it did not work the same thing happened. So, This time i tried to use system restore and i restored to yesterday when my computer was working fine, and well, now its working fine just like yesterday. What im just worried about is if there are any like side effects to system restore, like my hardware breaking, or etc.. I wanted to reinstall my OS again but it takes too much time. Am i just being paranoid about this? Please help im really worried about my computer breaking.