Best way of detecting if Windows has Windows Updates ready to download/install?

Question

I\'m specifically interested in Windows 2000/XP, but Vista/7 would be interesting too (if different).

I was thinking along the lines of task scheduling a batch file

Answer 1

I believe Windows updates are downloaded using the BITS service. You could use Bitsadmin.exe found in the Windows Support Tools. From the command line you can run bitsadmin.exe /list and you can see the status of BITS jobs. (i.e. download progress, job name, job status)