One method I have used in the past: Save ISO images of the CDs onto your HDD, then use software to create a virtual CD drive and manage the ISOs (I use Alcohol 120%), though IIRC there WAS a small free one released by MS.
However, there are drawbacks to this method (such as having to have extra software running in the background), and as Dazmatic pointed out
most games will have some sort of copy protection on the disk, which will require extra workarounds (such as cracks).
I'm not sure about the whole legality of this though, so I won't go into more detail here, but a google search should help