When I boot my Dell D600 it get a blue screen and

In this case, we need to reset the computer back to factory settings.
here we go...this process will cause data loss.
1. Remove non-essential peripherals
like
a) Scanner
b) Printer
c) Modem or Network cables
d) Personal Digital Assistant (PDA)
e) USB flash drive or other external Hard Drive
f) Any other external devices (e.g., USB-attached devices)
g) Remove the computer from the docking station, if you are using one.
2. Turn on the computer.
3. When the Dell splash screen appears during the computer startup process, press and hold <Ctrl> and then press <F11>. Then, release both keys at the same time.
NOTE: Some systems like Inspiron Mini 9 (910) do not support System Restore as they do not have <F11> nor any substitute.
4. In the Dell PC Restore by Symantec window, click Restore. Alternatively, press <Tab> to highlight Restore, and then press <Enter>.
5. When a warning message appears stating that all data will be lost, click Confirm, or press <Tab> to highlight Confirm and then press <Enter>.
The Progress window will appear. Once the restore process starts, Dell PC Restore by Symantec usually takes about 8 to 10 minutes to finish.
When the restore process is complete, the following message will appear:
The system recovery process was successful.
6. Click Finish or press <Tab> to highlight Finish and then press <Enter> to restart the computer.
The software is now installed as it was when the computer was first received.