Few days before, I posted that you cannot install Visual Studio Codename Orcas March CTP on Windows Vista, however, I got comments from Dustin and Paul who just did it! (Dustin used a VMWare virtual machine though).
Hmm.. I honestly wish I was wrong and I can use the new web features :S. But...
Well, it's not only me. Many guys in Channel9 forums confirmed it, and others in MSDN forums (like here, here and here) with different errors. Even the download page for the self-extract files does not include Vista in the supported operating systems. :(
I searched Microsoft Download website today for 'orcas march', and I got this:

Here are the facts (what each package contains is described here and partially in the official statement) :
- The 1st link
- is 9 parts for VS, and Team Foundation Server.
- The installation instructions deal with it as VPC image (nothing else says this, they treat it as default I guess).
- The supported operating systems on the download page include Vista.
- The 2nd link (that's what I tried before)
- is 7 parts for VS.
- is self-extract files (which matches the title anyway).
- The supported operating systems on the download page do not include Vista, and (from my experience) it fails to install on it.
- The 3rd link
- is 7 parts for VS,
- The installation instructions deal with it as VPC image.
- The supported operating systems on the download page include Vista.
- The 4th link
- is not VS at all. It's only 2 parts for TFS. The download page says it's TFS only in the title. It looks like it was truncated or so in this search page no more.
- is self-extract files (which matches the partial title appearing).
- The supported operating systems on the download page do not include Vista (Only include Windows 2003, as you'd expect).
So, these are simply your options when trying Orcas March CTP with Vista.
DIGG It