I don't know how the new PAM will handle the drive space but I have a suggestion.
In my VB6 version I used a picturebox control, and set picture to drive_space_slider.bmp(135x15 pixels)
On the form load I set the picture box width to
135-(drivefreespace/drivetotalspace * 135)
The drive_space_slider size should always be 135x15
The picturebox doesn't resize the image, it only displays as much as will fit in the box so you get the right size bar and no shrinking or stretching is required.
I don't know if delphi has a similar control, although I am guessing it does.