Restart Problem

Hello Sirs,

I have a dell desktop with very old specifications: 40GB HDD , 1GB RAM, and I have been working on this desktop using another hard drive with 250 GB, but suddenly the first hard drive(40GB) stopped from working, The Problem is that once I open the computer, the screen of “start windows normally” appears, and when i just enter it, it restarts itself.
unfortunately i have kept some important files inside.

What do you recommend me to do?

I appreciate your valuable advice.