DOS Beer: Only comes in 16oz cans. Originallyavailable from several breweries, they all tasted the same: bland. Eventually, people only bought DOS beer from a Micro-brew called Microsoft.
Mac Beer: Comes in 32oz cans. Allows you to drink multiple beers at once. A very tasty and attractive beer, however it lost favor with alcoholics for being a little "light". Only drinkable from an Apple brand mug.
Windows 3.1 Beer: Looks kinda like a Mac beer, tastes more like a DOS beer. Claims to be able to let you drink multiple beers at once. In reality, it's difficult to drink more than 1 without spilling all over the place and making a big mess.
OS/2 Beer: Comes in 32oz cans AND lets you drink several 16oz beers at the same time. Despite the fact that IBM claims millions of people drink it, you never see them, and no pubs sell it.
Unix Beer: Comes in 8, 16, 32 and 64oz cans. Available from several breweries, it's rumored to be very potent and the brew of choice for college students.
Windows 9x Beer: Looks like a Mac beer, tastes like a Windows 3.1 beer, smells like a DOS beer. Open the 32oz can and you'll find 16oz of beer. Cans tend to explode if drank from frequently. Since it's mostly a recreational brew, many people use it for drinking games, and don't mind it's shortcomings. Especially since they had to pay for it when they bought their fridge, whether they drink the stuff or not.
Windows NT Beer: Looks sort of like a Windows 9x beer, tastes sort of like a Unix beer that's gone off. When first produced, the 32oz cans were full of holes. They're still being patched to this day.
Linux Beer: Originally brewed by a Finnish university student as a cheap replacement for Unix beer. He gave away the recipe, and now many breweries make it, each distributing their own unique flavor of the brew.
Windows 2000 Beer: Windows NT beer dyed to look exactly like Windows 9x beer. Cans still leaky.
Mac OSX Beer: It's actually a Unix beer that just looks like a Mac beer. Initial versions didn't contain some key features (like alcohol) but it has been getting better with each batch. Still can only be drank from an Apple mug, despite some generic mug owners begging to try it.
WindowsXP Beer: Windows 2000 beer with a new label. It also has a new marketing scheme: Not only do you pay for it when you buy your fridge, you also pay for every day it spends in your fridge. You can't move it to another fridge, or rearrange the other items in your fridge, or it instantly becomes de-alcoholized and you have to call the brewery to get it re-alcoholized.