The other day I used a tweak manager (I don't remember what, unless msconfig, which I don't think) to uncheck some drives - basically the drives I was not using, hoping that it would make my computer faster.

But now a problem. Some things, many, are now greyed out. Does anyone know how to re-check the box next to these drive letters?

I hope so.

are you saying that you made it so that there was no drive letter for devices which should have one?

If so, and using XP, right click My Computer, select manage, go into disk administrator, find the hard drive partition or device, right click, should be a setting like "change drive letter assignment" or something - option might be ticked to not assign it any drive letter. give it the one you want. you may have to reboot your machine.