I guess I will ask - why don't you want Desktop Manager installed? (although, that might still not address your problems). If nothing else, it allows you to backup your phone and all of its data and settings?
What happens if you plug in the usb cord? Do you have Mass Storage Mode enabled on the Tour? Try another usb socket on your computer. Do not use a usb hub. There is also a way to make sure that your computer shows additional drives altho at the moment, I don't recall where you do that tweaking - it might be under Manage Computer = storage devices.
My windows xp machine will not see my tour unless I manually approve it to switch to mass storage mode...then it comes up as a drive under my computer.