F1 F2 is the BIOS giving you the choices, not Windows. Looks like the computer is not seeing the hard drive(s). Hit F2, check the hard drive settings, and boot priority options. Power off and back on, if it still persists, you may have a bad or loose hard drive cable, or the hard drive may have died.
Vista minimum requirements.
* 1 GHz 32-bit (x86) or 64-bit (x64) processor
* 1 GB of system memory
* 40 GB hard drive with at least 15 GB of available space
* Support for DirectX 9 graphics with:
o WDDM Driver
o 128 MB of graphics memory (minimum)
o Pixel Shader 2.0 in hardware
o 32 bits per pixel
* DVD-ROM drive
* Audio Output
* Internet access (fees may apply) Windows Vista: Recommended System Requirements
Personally I recommend at least 2GB RAM for Vista.