Why is it bad practice to install SQL Server to the root of a drive
Yes SQl server installation is likely to fail if you are trying to install it on root of a drive which is never advisable and has security implications. Actually it is related to permission setting on specific folders. As per this connect item 


  Based on further investigation this issue is due to the fact that SQL tightens the ACL for default data/log directories to exclude broad access for all authenticated users. If the drive root is chosen as the default data/log location then SQL will tighten the root ACL and thus effectively locking down the whole volume. The recommended course of action is to always use a subdirectory to store SQL data/log files.


So there seems to be problem with ACL's when installing on root of a drive in your case.