Boot Prob

hi
i recently bought a new pc (finaly my own pc)

MEDION AKOYA MD 8828
- Vista home premium (32bit)
- Intel Core 2 Duo Processor E6750
- NVIDIA GeForce 8600 GS PCI-Express
- 2048 MB DDR2 Dual Channel
- 500 GB S-ATA HDD
- Integrated WLAN IEEE 802.11n Draft

All basic programs were already installed on my Hard Drive when i installed my pc at my room and all seemed to work just fine...
Then i installed NFS:U2 (need for speed underground 2) and played it for some minutes, eventualy just to check out graphics and speed etc...
Then i shut down my pc and the next day when i started it up again it gave failure.
My oc didn't want to start up, i get first the black screen which says my AHC BIOS is installed and then i get the windows loading screen and finaly the black screen with the logo of vista. After this i should get a screen with the useracounts, but this one stays out! It just stays black^^.

Then i tryed with the dvd from vista with solving problems and then start-up problems but he can't find any.
After this i saw that in the first black screen there's written below : 'boot from cd rom'
So i tried to fix this in my BIOS with selected 'boot from HDD' but i simply can't get in my BIOS^^.
The only screen i can get is the one with options to start windows in safe mode... So i also tried this and this works! But being in windows in safe mode i can't solve my original problem and i simply can do nothing!

I'd be very happy if someone could help me out here...
I didn't change the 'boot from...' myself so it appeared to be changed out of itsself^^.
I don't know what to do anymore...

Tx in advance and i hope you understand what my problem is...
Grtz, a nAz who can't wait to get started with his new pc