Welcome to the PSR Tutorial Forum, Taters!
.rgt files are not Styles, they are Registration Bank files. To view and load .rgt files you must be in the Registration Bank Selection display. To open this, press both "Regist Bank -/+" buttons at the same time. After loading a Registration Bank, you can call up the individual Registrations it contains using Registration Memory buttons 1 - 8.
To view and load Style files you must be in the Style Selection display. To open this, press any Style category button (or, on SX900/700/Genos, touch the name of the currently loaded Style in the Home display) and navigate to the desired drive (e.g. User > USB).
Style files can have different file extensions, e.g.:
.prs = PerStyle
.sst = session style
.fps = Free Play Style
.scp = DJStyle
.sty = default style
.bcs = Basic Style
.pst = pianist style
.pcs = piano combo style
Hope this helps!
Best regards,
Chris