Spyware Guard is now NO LONGER available from Javacool - that is now Brightfort - I just wanted to confirm which your were referring to, as other products, some of which are very undesirable go by very similar names.
Even if it was, it was never updated to use with Vista let alone windows 7.
You must have used an old link download, and the site that hosted the download has not bothered to update it.
Here is the Spyware Blaster details, that have replaced the spyware guard
HOWEVER my opinion is that you should first examine exactly what is provided by your present anti-virus, as many also provide anti-spyware.
You may well find that Spyware Blaster works perfectly.
Conversely you may find, although it is not as such an active running process, so there is not a great chance that it will conflict in any way with your anti-virus, that it does indeed slow the performance slightly.
In summary, what anti-virus do you use? and if you wish try Spyware Blaster and see how the system runs.
Spyware Blaster has a reasonable reputation, but there are also reports of it not appearing to sit well, with some anti-virus protection.
Basically it is really a question of trying it out.