Generally you should be able to open the Window, drag it to full size, then click the Resize box in the top right (next to the red X) a few times to program it what size to open to.
You can also edit the shortcut to your program by rightclicking it and selecting Properties. From the listbox next to Run, simply select Maximized and then click OK.
My Computer
Computer type
PC/Desktop
Computer Manufacturer/Model Number
Custom-built
OS
Windows 7 Professional SP1 32-bit
CPU
Intel Core 2 Duo E6600 2.4GHz
Motherboard
Asus PL5D2
Memory
4GB DDR2-667 (4x1GB in dual-channel config)
Graphics Card(s)
nVidia GeForce 9800 GT
Sound Card
Creative X-Fi XtremeMusic
Monitor(s) Displays
Acer P236H
Screen Resolution
1920x1200 (DVI)
Hard Drives
OCZ SSD Vertex Plus 60GB SATA (Firmware 3.55), 64MB cache
Hitachi HD321KJ SATA, 320GB, 7200rpm, 16MB cache