You arn't booting from CDROM. Try hitting I think it was F12. It shows up on the Gigabyte logo, the boot menu is what you want. It will open a menu and go to CDROM. That will load Vista. If your problem is that Vista isn't recognizing your hard drive, then read on.
I talked to Gigabyte for 6 hours, and they just had their heads up their asses the whole time.
First off, if no drivers are showing up, that means your BIOS isn't set to ACHI mode. I don't have my computer on me, so I forgot where in the BIOS that was exactly. It was on the left column and 2-4 rows down. It was the very first option in that menu (originally set to disabled). Also make sure HPET is set to 64 bit mode (all other options were set to default). That should be enough to get drivers off USB drives and floppy disks recognized. For me though, that wasn't enough to get my hard drive recognized. I figured it out though. The South Bridge has problems detecting WD and Seagate hard drives that are unformatted/unpartitioned. The solution is to go to Western Digital's website, go to support, and under downloads, find your exact hard drive. Download the Data Lifeguard Tools for DOS (CD or Floppy doesn't matter) and put it on the CD/Floppy and boot your computer from that CD/Floppy instead of Vista. The actual program is buggy as hell, it took me 20 minutes to trick it into working. Get it to partition any amount of space, it doesn't matter as long as it is one partition. After you have a bit of it partitioned, boot from Vista. Once you get to the screen where you can pick which hard drive to partition, you should see your hard drive's partition (you don't need any drivers). Click on it and go to expand partition, and expand it to the whole drive, and reformat it. Make sure no USB drive is in your computer or else you get a weird error, and then it installs Vista just fine.
My system:
1 x Windows Vista Ultimate 64-bit
1 x NZXT TEMPEST Crafted Series CS-NT-TEM-B Black Steel / Plastic ATX Mid Tower Computer Case - Retail
1 x GIGABYTE GA-EP45-UD3R LGA 775 Intel P45 ATX Intel Motherboard - Retail
1 x HIS Hightech H487F1GP Radeon HD 4870 1GB 256-bit GDDR5 PCI Express 2.0 x16 HDCP Ready CrossFire Supported Video Card - Retail
1 x CORSAIR CMPSU-650TX 650W ATX12V / EPS12V SLI Ready CrossFire Ready 80 PLUS Certified Active PFC Power Supply - Retail
1 x Intel Core 2 Duo E8500 Wolfdale 3.16GHz LGA 775 65W Dual-Core Processor Model BX80570E8500 - Retail
2 x G.SKILL 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 1066 (PC2 8500) Dual Channel Kit Desktop Memory Model F2-8500CL5D-4GBPK - Retail
1 x SAMSUNG Black 1.44MB 3.5" Internal Floppy Drive Windows 98SE/ ME/ 2000/ XP - OEM
1 x Western Digital Caviar Green WD10EACS 1TB SATA 3.0Gb/s Hard Drive - OEM
1 x Acer P243WAid Black-Silver 24" 2ms(GTG) HDMI Widescreen LCD Monitor with HDCP Support - Retail
1 x Logitech MX518 2-Tone 8 Buttons 1 x Wheel USB + PS/2 Wired Optical Gaming-Grade Mouse - Retail
1 x ASUS Black SATA DVD-ROM Drive Model DVD-E818A3T - Retail
1 x Creative Sound Blaster SB0570 Audigy SE 7.1 Channels PCI Interface Sound Card - Retail
1 x Arctic Silver 5 Thermal Compound - OEM
1 x ZALMAN CNPS9500 AT 2 Ball CPU Cooling Fan/Heatsink - Retail
1 x Rosewill RFX-100B 90mm PCI Slot Case Cooler - Retail
1 x Logitech Z-4 40 watts 2.1 Speaker - Retail
Good luck.