How long ago was that? Virtualisation is a lot better now, I've found Fusion a lot better than Parallels as well. Though I'm somewhat biased against Parallels due to the piece of shit they refer to as Plesk for Windows. Plus we are heavy users of VMware ESXi at work which we seldom have any problems with.
You need plenty of ram as well, 4Gb isn't enough to run side by side but 8Gb does the trick (even more would be better).
I do only have 4GB of Ram, but it wasn't the speed or stability that I found a pain in the arse, it was the whole pointlessness of loading a virtual machine within a machine. I eventually found, or at least learned, I had no use for it, as I slowly found a means of achieving the same results while remaining within OSX.
For a while I did still, on occasion, use Notepad++, but I refused to use Fusion just for that and found CrossOver. CrossOver is like a Windows Emulator and requires no Windows OS, it sort of converts an exe to an app and works in much the same way (albeit taking longer to load). To be honest, I don't use that anymore either.
And for any Mac users who don't own LaunchBar yet, buy it. (It's like QuickSilver only better. Everyone should own it!)
http://www.obdev.at/products/launchbar/index.html
