1) None of the programs (barring a few "special" ones that do not share the OS resources) will run from the old disk. You will have to re install them.
2) Data files can be opened by the corresponding programs where ever they are located. You can have Excel in D drive and the xls files in another drive.
What I would do is backup my data files to the first drive, and also those "special" programs.
To your last question, the answer is NONE.
I'm putting a 2nd 40 gig hard drive in a new computer I have purchased. This hard drive is from my old computer that had the motherboard fry last week. This old hard drive has winxp on it and quite a few programs/files saved. What I want to do is get rid of a bunch of garbage off this drive that isn't needed.
Does this drive have to have programs such as word/excel installed on it if I save the data files there or can I delete it off the old drive and just have it on my new one? Or do each drive have to have the corresponding program installed to open it?
I guess my question is if this were you, and you were going to have all of your programs installed on the new drive, how many programs are necessary to leave on the old one?