When my wife bought her Inspiron 1525 (with Vista Home Edition) about two years ago, she experienced the problem that has been discussed in several threads in this forum: the computer would immediately wake up again after being put on sleep or hibernation. At the time, we managed to solve the problem by changing the energy managment settings for the wifi card (as discussed in the thread at http://en.community.dell.com/forums/p/19200878/19326503.aspx and elsewhere).
We still have no problem putting the computer to sleep or hybernation. However, during the last few weeks, the computer has occasionally been waking up by itself, for no apparent reason. I suspect this could be related to some software update?
I've checked the wifi setting and they are still set the way they should be.