VM Ware Fusion all the way!
I bought parallels when I first got my MPB but it slowed down my system and I didn't like most of the tools, etc.
At some point VM Ware was offering $20 to buy if you switched from parallels to Fusion, so I did. Love it!
And no you don't have to own a PC to use it you just install windows on a partition, or in boot camp if you wish(the great thing is it can open a boot camp partition while in Mac OS X so you never have to leave your lovely Mac to do anything with Windows.
You will have to buy a copy of Windows if you want to run it legally although it will install from a disk image if you download one.
It's basically just perfect.
Now I only use it as a testing ground to make sure files or programs I've downloaded don't have malware before sending them to a Windows user but if you really need to run Windows on your Mac VM Ware Fusion is the way to go!