Taras Glek, from bugzilla.mozilla.org, found a way to trick Windows into loading Firefox faster by using a simple patch.
Basic idea is that the sequential flag + bull**** read tricks windows into reading xul in Mb chunks instead of stupid 32k(or smaller) ones. Have to do it this way because there is no fadvise() on Windows(that I know of) A big sequential read cuts down on a lot of seeks.
Many users are reporting faster boot times, with load time cut by 50% on slower drives. If this work-around proves to work for the masses, it may be rolled out in the next version of Firefox. Currently, there are users looking to refine the process to make it even more efficient.
When trying out any experimental technique, you are cautioned to do so at your own risk. This patch has not been verified to work on all versions of Windows, but the general response so far has been very positive.