There are a lot of people that afraid to switch of Vista because they are afraid that their stuff will not work. Well truth be told, I've been running Vista+VS2005_SP1+PB6 since March of this year and haven't had any major problems. The only two problems I had was:
1. If the device doesn't have Vista compatible driver then you will not be able to connect/debug the device.
2. Flashing the devices on Vista can be painful because some devices still have no support for Vista flashing.
In order to have this properly working you need to uninstall PB5 from your machine before installing PB6. Personally, I would use a fresh Vista install.
After you install Vista and Visual Studio 2005 on you development computer, you need to install VS2005_SP1 which can be found here:
Ignore all the warnings that Vista will give you about VS2005 being incompatible with Vista.
Install Vista update for VS2005_SP1 from here:
Now you are finally ready to install PB6 and PB6_SP1. Follow this link to install PB6:
I know this might seem like a lot of work just to install PB6 but trust me the benefits that you will get from using PB6 will outweigh this cumbersome install. Just the ability to use mismatched PDB files does it for me. And also full integration with Visual Studio is a very nice addition.