I have never owned a laptop, so not sure how they fit together. If I buy a 2001 laptop that has a Floppy drive, is it likely I will be able to pull it out and replace it with a laptop DVD/CD combo drive, in very the same place? Is it possible that the dimensions of the DVD/CD drive will not match or that the connectors inside won't be compatible?

Theres about a 99.99% chance that the floppy and dvd driver will NOT be compatible. Swapping parts for the same part is usually ok but not for different things like floppies and dvd drives.

Chris.

Usually the only things that are interchangeable between brands are hard drives and memory, provided they use the same kind of memory. Within the same brand, models around the same year might be compatible, but it's really a gray area. Most manufacturers use a unique connector and design of some sort for their batteries, optical drives, and floppy drives, which isn't compatible with any other manufacturer (some exceptions exist I imagine, such as where one company owns another, or both get their laptops made by a third company). Some even use different connectors for different models, mainly so they can sell the same dvd-rw for their low end laptop at a different price than for the high-end model. So, the answer is, most likely no.

EDIT: just re-read your question. That all depends on the manufacturer, but most use a bay system that allows you to purchase a cd/dvd drive (or hard drive, or second battery) to go in the same slot. You do usually pay a premium price no matter what though, but hey, ebay works wonders