Thats really odd that your mobo's sata drivers are not supported by 7.
Its quite simple, I do it often. Go to Asus' website and go to Support, then drivers section. Input your motherboard model. Find the Sata drivers and download them.
The ideal scenario is if you have a floppy drive. Depending on the driver you download you will either have an executable which will give you an option to "Make Disk" or it will extract the files to a directory which you will have sub directories of x86 and x64. Copy the contents of those directories to a flash drive and plug it in before starting the installation.
At the hard drive selection screen where you don't see any drives, there is a text link that says load driver. Point it to the directory and it should give you a list of drivers to chose from. Chose the appropriate one until you see your drive listed.
If something I said here was not clear or you need it elaborated, please specify.