I don't know how to edit skins and I don't want to ruin it.
Can someone edit the default skin 'Aero Glass' so that when a windows is maximised, the frame dosen't look grey, rather as though it weren't maximised.

just get another skin. aero-glass skin looks pretty good.

actually, just right click on the TT icon, then choose skin and then choose aero 1 or aero 2. the frame shouldn't be gray then.

I don't have those.

ok, just download another theme then...