There are a number of factors that will effect the amount of time it takes for the GPS to get a lock.. If the window you are next to has any kind of metallic film embedded in it, you can forget it.. and while your window may have a nice view of a section of sky, you may still not be able to 'see' any GPS satellites.. The best thing to do is to go outside....

I own a Garmin Nuvi 660, the N810, and the N95-1 and -3...

(I also own the N800 and a pile of other misc. devices too numerous to mention... I MAY have a problem.... :-) )

The Garmin gets a lock nearly as soon as it is turned on.. It IS a purpose built device and its' circuitry has better 'location' options built into it..

My N810 gets a lock in my car in about 2 minutes from the time I start the Maps application.. It DOES help that I own a convertible and even when the top is 'Up' it is radio-transparent...

The N95s take a bit longer, but will get a lock in about 2-3 minutes...

The Initial N810 GPS lock took about 15 - 25 minutes outside.. I had the thing turned on in my office next to a window for hours with no luck... but once outside it worked well... subsequent 'locks' now occur in about 1 -2 minutes.. If I take the thing across the country, I would expect that I would have to wait for 10 -20 minutes to get a lock in the new location..