If you didn't specify sizes of anything, the page should just cope. You probably need to go in on the HTML view and remove all the specific sizing where it doesn't matter. In short, you don't have to redo the whole site: only bits of it.
A lot of the design depends on how people view websites. Some always run the browser fullscreen. I hardly ever run anything fullscreen. Just personal preference. As a result, when things are in fixed positions on the right, I can actually miss them because they are not visible. If you ever have to stick anything on the right, make sure it is not important.
In theory, good websites should be able to cope with 800x600 (minimum XP resolution). Having said that, many designers don't bother so you end up with half the website visible on an 800x600 screen. The minimum that most cope with is 1024x768 (minimum Vista resolution). This is absolutely crap for notebooks which have a resolution of 1024x600.
Since there are not that many 800x600 notebooks about (I am the only person I know who still uses one regularly), you can probably base it on 1024x600 as the minimum you ought to cater for. This will be good for netbooks.
Many people don't mind scrolling vertically but somehow scrolling horizontally annoys them.
Also view on several browsers: not just IE, unless it is an intranet and the only browser is IE.
You can download virtual machines from
The great thing about these is you can set the max screen resolution, run the browser fullscreen and see immediately what the result looks like.