The problem here is deleting files in folders to free space, the files often in folders are used by other programs for other purposes and have little of any size or consequence to downloading any other files to your PC and rarely have enough MB to make a difference.
You never should have even bothered deleting files from any folders, this is a sure fire way of getting many multitude of system error and file load error.
You should always start by going to disk cleanup and doing the clean up to free space.
Then to defragment and free up more space there.
Then to Add and Remove Programs to remove applications you no longer use or need.
The main thing is if you have a limited or inadequate HDD is you take up relatively all the space in your Pc quickly with files, songs, games, and applications and it takes no time, even one or two movies and a warning comes up and you have no space.
But, the reason you got this message is easy, you deleted a group of files and maybe the PC needs these files, but in the group you delete without using uninstall or any other process to safely remove the file needed to be removed you choose to haphazardly delete it, ad get the warning, You do not have write access to do this application since your PC needs those files.
So, you need to stop and figure it out and fix your errors or you will end up taking it to the shop so they can fix it. Which honestly will not be long from now.