You hafta use SETool 2 Lite (Download) which is IMO the best and easy way to flash SE filesystems. It supports W200 but I am not sure whether flashing filesystem would properly work in it and what are the default directories for W200... Its best if you search for flash themes and how to customize and upload such themes into phone GDFS filesystem in forums such as lasyk and SE-NSE befor you attempt to do such a thing. I have successfully used XS++ as well as SETool2Lite on my W850i and uploaded lots of flash themes..... and they both worked fine....
WARNING: Incorrectly flashing and tampering with phone filesystem will brick your phone.
Heres the lasyk forum for W200:
*myforum.lasyk.net/forumdisplay.php?f=51
Heres the excellent tutorial by Waldog and another free method by ybtan, which helped me successfully customize my W850i which is running flash themes now...
*myforum.lasyk.net/showthread.php?t=32889 ------ NOT FREE !!!
*myforum.lasyk.net/showthread.php?t=35532 ------ USES XS++ and FREE