Achara29 wrote I've a second hdd 3.5" ready to go but I've not rails to install it into the bay properly. Does anyone know if i was to just sit it in there lying/standing would there be any issues?

The problem with doing that with a standard HDD is that it can vibrate and move around. Not to mention lets say your dog sprints around the room and knocks over your tower, your HDD could take more damage than it would if it were properly mounted. Personally, it's not something I'd do. 3.5" drive mounts are cheap, I would buy a set if I were you.