Just think about it, you have answered your own question. The second CD (with the drivers) these are for your old machine. The new machine will have drivers for Vista. You have no driver disc for XP devices for the new machine.
Also how did you acquire Word, Excel etc. If they are retail versions then you have no problem at all with these. Older versions will work with Vista, just install them. And despite what many may say, to go back to XP is a retrograde step. Vista is superior in every way. I do not understand the blinkered atitude of many on this forum. All I can say is that they have never tried it properly.
To clarify, if your coies of Word etc were supplied with the old machine, then they are very likely OEM versions, which ties them to the machine they were supplied with. It's a common misconception that people actually pay for software. They don't. What is paid for is a licence to use that software for as long as the terms of the licence are adhered to. Break the terms you lose the right to use it. Ownership of software always remains with the developer/vendor.