Vista is a totally unreliable and unpredictable operating which still has more bugs than any other Micosoft operating system in history. It is resource hungry and is frequently incompatible with industry standard software -including some of Microsoft's own!
Commercially it is has been a failure with large commercial sites "downgrading" to XP Pro in preference to perservering with the unreliability and inconsistencies with Vista which inflated their desktop support bills but up to 70%.
Windows 7 will be released in October 2009 - we have been trialing a pre release version on 100 of our desktops for the past 4 months and it is working wonderfully.
I would suggest you ditch Vista when Windows 7 is released or downgrade now to XP Professional.