If you purchased the program Power DVD (from Cyberlink), you can reinstall it from the CD you purchased. If you chose the download-only from Cyberlink, you can contact them and request a fresh download. (You'll need proof of purchase, such as the confirmation e-mail, to do that.)

If the program came pre-installed on your computer, it depends. First, check the System recovery CDs/DVD that came with the computer (or you had to burn after setup)...just browse them using Windows Explorer. If that doesn't pan out, go to the PC manufacturer's website and see if they have the download available. If it's not on their website, contact your manufacturer using their support channels, explain the situation, and see what they can do to help. The should be able to give you the download so you don't have to reinstall Windows to get it back.

It would help if we knew the make and model of your computer, but those are the general instructions.

Hope this helps,
John