well done - I can see that a lot of hard work has gone into this. The colour scheme is perfect in my opinion, and the layout is clear and easily understood - an excellent illustration of how less can be more.
Ready for a couple of nit-picks?
1. You haven't put a copyright claim at the bottom of your pages - not essential, but highly desirable.
2. On a site that is (at the moment)predominantly about Windows software I would advise you to acknowledge the Micorosoft trademark specifically. "Windows® is a trademark of Microsoft corp." - something like that - placed at the bottom of any page that contains the word Windows and/or screenshots.
3. I only looked at the slipstream guide but on that page the text is too tight to the image border. Looking at your code you have both the cell padding and spacing set at 0 and I think your page would look less tense if you increase these settings. Experiment, but I think you may find there's an improvement if you set both at 3 or 4.
4. There's no 'Home' button on the inside pages - essential in my opinion. Visitors feel disorientated if they have to rely on the back button.
An excellent site - I wish you well with it. Where's the link to our forum?