By far the best free ISO mounting tool out there is Pismo file mount.
- Works great on Windows Vista/7 x64 (not natively x64 but completely compatible)
- Drives only exist when an ISO is mounted and are removed when there is no ISO mounted
- Small memory footprint
- Has simple minimalist right click shell integration
- Unattended installation
- No Branding or silly logos to speak of (very clean professional feeling program)
- Fully featured command line control that is automatically working right after unattended install
- Plus all the normal features you would expect from an ISO mounting tool
- Free for corporate use
Some things you will want to pay attention to though is that by default it will not mount the ISO to a drive letter but instead mount it to a UNC path which can cause some software installers to fail when installing from the mounted path. Just make sure you specify that you want Pismo to mount to a drive letter when you are doing the mount and it will work fine.
Here is the unattended install of SQL to demonstrate my real world use of Pismo.
SET MSDNIsoPath=\\itapp\ISO Library\MSDN
SET pfmMount=pfm mount -m %MountPath%
SET pfmUnMount=pfm unmount
echo -Installing Pismo File Mount
echo Install and configure Microsoft SQL Server 2005
echo -Installing Standard Edition
%MountPath%\Servers\setup.exe /settings "%ScriptPath%\Configuration\Microsoft SQL Server 2005.ini" /qb /norestart