http://bugs.winehq.org/show_bug.cgi?id=26803
--- Comment #2 from Paul Romanyszyn pgr@arcelectronicsinc.com 2011-04-18 23:13:42 CDT --- I have notices the very slow select a long time ago using registax4 from http://www.astronomie.be/registax/download.html I found a workaround using drag and drop. I just tested with a new install of registax 6 and it is slow. With this program the file dialog has a image preview. It appears that every time the file list edit box had an item appended the dialog does a paint refresh.
I don't have a windows machine to check how slow it is on windows but as I recall running 98 or XP under qemu was much faster.