upgrading to windows 98se

I have an older version of windows 98 . My son got some digital photo hardware and software for christmas that requires usb ports which my computer has but my version of windows doesn't support usb. I purchased a copy of windows 98se that does support usb. When trying to load the new version the setup cannot be completed as an error message(su0409) appears stating I must disable my antivirus program.I then removed norton system works 2003 from my computer and tried again.This time the message stated I could'nt complete the setup until I load windows upgrade.Where do I go from here?

 

Start the computer with a boot floppy, choose with CD-Rom support. Watch for a message giving you the drive letter for the CD, it will not be the usual letter, use it for the X below. At the A:\> prompt, type in these commands, pressing Enter at the end.
ren c:\windows\win.com win.old
X:\win98\setup