Sizer is a freeware utility that allows you to resize any window to an exact, predefined size. This utility is very useful when designing web pages, as it allows you to see how the page will look when viewed at a smaller size. Another use of this utility is when you want to take screen-shots for documentation, using Sizer allows you to easily maintain the same window size across screen grabs. Once installed the utility runs in the system tray and can be configured.
There are three predefined window sizes available, these are the default ones, but you can add more resolutions based on your need.
When you want to resize and window, right click on the bottom/top portion of the window and select the size. Unfortunately Sizer is not supported under Windows Vista. There are issues installing the program and using interactive sizing.
Download Sizer (Windows XP)