If we are talking windows I can confirm the main body of the glass doesn't leak but all the edges can, the windows probably need adjusting. Puffing some talc around will leave tracks where the waters running from and to but not always where its actually leaking from but a good indication. Normally its either the front leading edge seal or the top seal to the hood/hardtop, the top seal in my experience being easier to fix.
Go to mgfcar.de for good info on what each adjuster does, they go from A to G (or H, I can't recall), it seems daunting at the first attempt (and 2nd,3rd......) but is very satisfying once mastered.
If its water in the boot its 10 to 1 the seals around the rear lights and again talc will confirm this, Good Luck