DVD computer problem?

My computer has been running rather slowly recently, so I went through and deleted and unistalled what I took to be unecessary files. After doing so I discovered that my computer could no longer play DVDs. I looked through the recycle bin and the necessary files are not to be found. Whenever I play a DVD in realplayer or WMP it says I have insufficient codecs, and when I try to download them I am told my computer doesn't have the capability to play DVDs. I don't have access to the original drivers or CDs that came with the computer. How can I fix this problem?