You need to have one volume (you can create multiple volumes on a single partition, you are not limited to 4 volumes) that is accessible from all your windows installations. This can even be a USB drive if you want, but it doesn't have to be.
You now have a few options.
Option 1: Consistent Mountpoint
Assign the same mountpoint to the common volume in all Windows installations. Lets call it G:. Then everyone can use G:\dev
This is simple (and effectively no different than the USB drive idea)
Option 2: Junction Points:
Again, assuming you have some volume that all your windows installations can see, you can use junction points.
It may be slightly tricky to set up, but it allows you to point a folder to some other location (the same way C:\documents and settings redirects to C:\users in Win7 and Vista).
Suppose each of your windows installs boots up, and sees its own volume as "C:" (but has a different letter visible from other OS installs). Also, suppose you want the folder "C:\dev" to be your source code directory on each of the windows installations.
You can create a junction point called "c:\dev" in each of your windows installations to your dev folder, wherever it is (even if its on G:).
That way, every install use the same path ("C:\dev").
Alternatively, you have:
Option 3: Virtualisation
You can create a VM to host all your dev environments, or you can create VMs to test different operating systems in. That will free up your disk configuration, and avoid test software interfering with your Windows installation(s).