I don't think that I have a Y drive that is for anything else. The colour of the question mark was blue. Although it has dissapered now.
Check your Device Manager. That article linked by Tony gives a workaround in the last post for mysterious drives appearing.
Basically uninstall any disk drives that you don't have or don't know in there and reboot. Windows will detect new hardware and reinstall drivers as needed.
I had a similar issue with my multi-card reader which appears as 4 regular drives (which is OK), but it used to have a fifth one with a question mark. Turned out it was its Bluetooth that needed disabling as you can only use 1 Bluetooth stack at one time and I allready had one - my keyboard and mouse.
I disabled that in Device Manager and all is OK now.
Sometimes it's a bit complicated sorting these things out, best ask a PC specilist forum as it isn't really a McAfee issue.