I can't really fix things just for "windows vista" alone. As far as I know, the OS has nothing that would effect all browsers in the way you are describing.
If you are using a specific browser or an outdated browser (IE7 for instance) I would suggest upgrading it so we can properly diagnose things.
I don't know what all you have modified so far but it looks like there are some odd inconsistencies with page size. For now, you can fix the sidebar on the woo commerce pages with:
#top.woocommerce-page .sidebar.sidebar2.box {
left: 972px;
top: 49px;
}
Transparency may not work exactly the same on all browsers and versions depending on how it gets added in. Using RGBA as you have will not work on Internet Explorer 8, 7 or 6 and older versions of Firefox and Opera.
For the main sidebar with the logo, you added the background color with RGBA which is why you don't have the space at the top. One way to get it back would be to re set the sidebar class as having a transparent background with:
#top .sidebar {
background: transparent url(../images/skin-minimal/bg-trans.png) repeat 0 0;
}
You can change font colors in the Theme Options>Styling.
The contact form can't have the effect you are describing without completely customizing it. You can look into using other contact forms via plugins that may get the result you are looking for.
Regards,
Devin