Most nuvi models including 2xx5 series can be updated with a GCD file that way. In fact you can also do it a few other ways:
1. Connect the unit to PC, drag nuvi24x5and25x5_GCDFile__810.GCD onto the WebUpdater icon on your desktop and it will load the file as gupdate.gcd in .System.
2. Put gupdate.gcd in a folder named Garmin in the root of a microSD, insert in nuvi then boot it but first remove any gcd file from the unit if present.
3. Make a file xxxx01000zzz.rgn from the gcd file using RGNTool [where xxxx is your HWID and zzz is the firmware version], drag it onto updater.exe and flash it in preboot [also requires removal of gupdate.gcd from unit if present prior to flashing though or it may reflash].
For a unit which cannot be flashed easily by usb, or the internal file system cannot be accessed by usb because of a loose or otherwise faulty usb socket for instance, there is also a method using SD using boot.bin as ldr.bin and commands in update.txt to both delete an existing gupdate.gcd and load a new one to .System. See [Only registered and activated users can see links. Click Here To Register...].