Ever been partway through a huge download, and Windows sends your PC to sleep, forcing you to start again? We have the answer.
The problem is in applications not being written with Windows' sleep APIs in mind. Firefox is a huge culprit, having not been compliant for at least six years.
Built for Windows 7 and Vista, Coffee is the answer to your prayers. It monitors a specific network interface, and, if it detects downloading or uploading at a higher rate than the user sets, it prevents the computer from sleeping. Setting the threshold to 0 tells Coffee to stop monitoring.
Once set to run with Windows through the Extra tab, it'll sit in your system tray, making sure you don't suffer from broken downloads again.