These will not be the responsibility of Gateway or Microsoft so don't call either. Instead look for the drivers for motherboard, video, audio, modem and what you have before the upgrade and collect these so you have them ready.
If you find there is no driver for a modem then you have to decide what to do about that. If you don't use the modem, then remove the modem. If you need a modem then the cost to upgrade to XP may include a new modem.
Hope this helps,
I am presently trying to upgrade my computer from Windows ME to Windows XP Professional. I have a Gateway computer with 127 MB RAM Intel(r) Celeron(tm) processor. My driver date is Nov 2000. It shows the Manufacturer Model Number ST320410A. I contacted Gateway for advise. The email I received said that I would need to purshase updated drivers. I then contacted Online Chat with Gateway and was told everything was compatable but that I needed to purshase more memory. I did a clean install of the Windows XP Professional and it seemed great except for it didn't show I had a modem any longer, so I had to put Windows ME back on. How do you manually erase the hard drive and do a clean install for Windows XP Professional and have everything work?