I know everyone loves OS X, but sometimes...., sometimes you need that other os.

Your lucky if you have a macbook or another intel mac.Because you can do it quite easily.You even have 3 different ways to achieve it.

1. Bootcamp
Download bootcamp and run the utility, an extra partition of 5GB will be created on your hard-disk, where you can install windows.(you will need a recordable cd to put the drivers on.
Now you can reboot into windows!

2. Parallels Desktop
Download parallels and install.
You can either make a virtual disk or use your bootcamp partition.
The nice thing is that you don't even have to reboot. (1 Gigabyte of RAM is recommended)
Just run it while your OS X is booted too!

3. VMware Fusion
Download VMware and install.
Again you can make a virtual disk or use your bootcamp partition.
This one doesn't need a reboot either.. (1 Gigabyte of RAM is recommended)

Remember, that windows is vulnerable to viruses and mall ware.
Even when it's running on a Macbook.