I downloaded Visual Studio 2008 professional RTM and tried to extract the file en_visual_studio_2008_professional_x86_x64wow_dvd_X14-26326.iso using 7-zip but the only file I got was README.TXT with the following content:
This disc contains a "UDF" file system and requires an operating system
that supports the ISO-13346 "UDF" file system specification.
What I then did that solved this was to run Microsoft Virtual PC 2007 and dragged the ISO file to the CD/DVD icon and then I could drag and drop all files from the virtual PC to the host computer.
Update. A friend send an email and recommended a couple of alternatives. I only tried the first one below.
Virtual CloneDrive is a freeware that virtually mounts the ISO to a drive and it worked great in Vista with the VS 2008 ISO. No 64-bit version yet though.
DAEMON Tools Lite is a freeware that supports both X86 and X64. Be aware that you might want to don't want to or want to uninstall DAEMON Tools Searchbar and Save Now that is included.