fix computer errors

My PC, Intel Core 2 Duo 2.93, 2GB RAM, GeForce 8400GS 512MB, keeps restarting. It says that it did not start successfully. In there it shows these options:
Safe Mode
Safe Mode with networking
Safe Mode with Command Prompt
Last Known Configuration
Start Windows Normally
When i choose “Safe Mode” it loads file like
multi(0)disk(0)rdisk(0)partition(1)\wi… All files are .sys like ftdisk.sys or pci.sys.
Then asks me to “Press Esc to cancel loading SPTD.sys” When i don’t press it shows another:
“Press Esc to cancel loading vax347b.sys” and when i don’t press anything. Restarts.
Same goes for Safe Mode with Networking and Safe Mode with Command Prompt.
When i try Last Known Configuration it goes to the Windows Logo and loads with the blue bars running then suddenly it goes to Blue screen the restarts. I disabled automatic restart when failure occurs. Then tried using Last Known Configuration, goes to windows logo, then It says on the Blue Screen:
A problem has been detected and Windows has been shut down to prevent damage to your computer.
UNMOUNTABLE_BOOT_VOLUME
If this is the first time you’ve seen this Stop error screen, restart your computer. If this screen appears again, follow these steps:
Check to make sure any new hardware………………..
Technical Information:
*** STOP: 0×000000ED (0×89DB6900, 0xC0000006, 0×00000000, 0×00000000)
Same goes for start windows normally.
This type of error occurred only w/out the Blue Screen of Death and i can use Safe mode on my old desktop. I bought a new one after two months buying a new one this is the problem.