Umm...
Umm... Your Acer Aspire came with no OS? Did you buy it used? This one came with Vista and runs perfectly. Anyways, boot from your Vista disc, enter your language, currency, and keyboard output. Then press "Start Now". You should now see a screen that has "Install Now" on it. In the bottom left hand corner, there is a button that says "Repair Your Computer" or something like that. Press it. Then press the button that says "Startup Repair". Hopefully on reboot you will reach the desktop. Post back with results.