Non proportional Font

[searaven]

Have a simple application to compare command strings agianst typical patterns and I use a text string on the form as an example. Using Monospac821 BT and it looks fine on my machine and others but on one laptop it's definitely not proportional and is skewed to the left.
Here's a XAML snip:
<Label VerticalAlignment="Center" Foreground="DarkGray" FontFamily="Monospac821 BT" FontSize="14" Name="Lbl1" FontStretch="UltraExpanded">
RNGE UPDATE YYYY-MM-DD AA121AAAAA ZZ121ZZZZZ P##### </Label>

Any ideas what could be causing this? I'm think graphic chip maybe?

Any help/ ideas apreciated...