Installing to C:\ProductName
Some applications need to be installed to C:\ProductName or something similar, but 99.9% (if not 100%) of the examples in the net install to C:\Program Files\CompanyName\ProductName.
The following code can be used to set the TARGETDIR property to the root of the C: drive (taken from the WiX-users list):
TARGETDIR=""
TARGETDIR=""
NOTE: By default, TARGETDIR does not point to C:\! It rather points to ROOTDRIVE which in turn points to the root of the drive with the most free space (see here) - and this is not necessarily the C: drive. There might be another hard drive, partition, or USB drive!
Then, somewhere below your tag, you need the following directory tags as usual: