This means you installed Office 2010 using Click-to-Run. Click-to-Run is based on Application Virtualization technology. The Q:\ drive is the virtual file system drive where virtualized apps "live" in the file system namespace. The Q:\ drive is not a real drive; it has no space and is not accessible from Windows Explorer or "My Computer".
Any access to the Q: drive, including hiding or deleting it, has been removed.
See this: http://office.microsoft.com/en-us/excel-help/click-to-run-switch-to-using-an-msi-based-office-edition-HA101850538.aspx?CTT=3