You've not stated how you normally transfer pictures from your camera to your PC. If you do so by connecting the camera directly to your PC, you're definitely doing things the hard way. A USB card reader is far more flexible. It's also what you need to transfer files from a CD to a memory card.
If you've not got a card reader, now's the time to get one. (Amazon have plenty for under a fiver, but you could also try Asda or Tesco Extra).
Once you've connected your card reader, and inserted the memory card, the card can be read and written to, just like any other drive. Assuming that the CD is already in the relevant drive, double-click on 'My Computer', then double-click on the CD-drive icon. (If necessary keep double-clicking until you've opened the folder where your pictures are located). Ensure that the open window only occupies part of the screen.
Now double-click on 'My Computer' again. Then double-click the drive icon for your memory card. (There will probably be several drive icons, for different types of card. Just double-click each one in turn until you find the one which doesn't say 'Please insert disk'). Once you've opened a window to display the card's contents, ensure that it only takes up part of the screen (so that the CD and card windows are side by side on your screen).
In the CD window, click on one of the files you want to transfer across to the media card. (If you only see a list of file names and can't remember what each picture looks like, go to View > Thumbnails). While holding the Ctrl key down, click on any additional pictures you wish to transfer. Then click on any one of the selected files and, while holding the mouse key down, drag the files to the other window. Job done!
Chris