Was previously using a WD EIDE drive on vista/core2duo E8400/Asus 5QPL Pro.
Bought samsung SATA2 drive, plugged it in, removed EIDE connections, booted and it said HDD not found, press F1 to resume. It shows in the BIOS setup screen, but won't boot to it. Put a win7 beta CD in to do a fresh install, recognized HDD with around 430GB unallocated space (500gb drive), tried to create a new partition and it failed. Win7 said it couldn't install onto the CD and to check in BIOS if the HDD was set to boot.
Start by checking your BIOS settings. You were using an EIDE drive, now have removed it and installed a SATAII drive, planning to install Win7 Beta on it.
On many systems with support for both EIDE and SATA drives, the BIOS default settings were to Enable the EIDE ports and Disable the SATA ports. To use a SATA drive you have to Enable the ports. Then the next step. I don't know about Win7 Beta, but some earlier Windows did not have drivers for SATA built in - only IDE. So the install disk could not access a SATA drive. A solution many mobo's used was an option in the BIOS to have the on-board SATA controller emulate an IDE drive, so that Windows could deal with it without even knowing it was a SATA in disguise. Look for such an option in the BIOS. Then also look for a place to set the sequence of Boot devices, and make your new SATA drive the second in the choice chain (the first will be your CD or DVD drive, where you will place your Install disk).