i need to reboot from a 3.5 diskette to update my cd-rw driver, but although i make a cold reboot with the diskette inside, the pc starts normally win 98 without reading the diskette. that happens with every diskette. the diskette units works perfectly and the diskette is in good conditions. i remember i had to push some key while w 98 is starting and then change some option to make the pc read the 3.5 unit to make a real boot start.

i have:

dell dimension xps t 550
w98
128 ram
12.7 gb