JFX has made a nice tools that automatically extracts imagex, bcdboot and various others useful files from the Microsoft Windows Automated Installation Kit (WAIK) across the internet so that you do not have to download the >1GB WAIK installation ISO and then install it just to get a few files!
I recommend you pick the Win 8 Waik Tools!
(Waik Vista and Waik Win7 does not download bootsect.exe.)
The tool can be downloaded from the link on this page - it can also be directly downloaded from this site by clicking on this link.
Tick the options that you want and click the Download button. Once completed (the Windows 8 option shown takes about 30-60 seconds), you will have a set of folders located beneath the folder where the GetWaikTools.exe program was located.
waik_2 for the Vista WAIK tools (does not contain bootsect.exe)
waik_3 for the Windows 7 WAIK tools (does not contain bootsect.exe)
waik_4 for the Windows 8 WAIK tools
waik_4_1 for the Windows 8.1 WAIK tools
Here are the WAIK4 (Win8 WAIK) files extracted (there will be folders for each WAIK version, x86, amd64 and sometimes ia64)
GetWailTools.exe can also be run from the command line and so can be used in Windows batch files - e.g. to get all WAIK files...
start /wait GetWaikTools.exe -win7 -win8 -vista -win7Dism -win8Dism -silent -cURL:0 -ontop:0 -folder:WAIK
JFX's tool does not extract the winpe.wim file. If you want to extract the Windows 7 WAIK3 version of this WIM file (for instance to modify it and use it as a boot.wim winpe boot file) you can use the getWinPEWIMs.cmd script. This download uses Nuno's re7zip.exe utility and 7zip to extract some chm help files and the winpe.wim files.
If you need to add extra components to the winpe.wim (e.g. languages, wmi support, scripting support, .Net, etc.) then you will need to download and install the whole WAIK.