Getting stuck in a reset loop. reset, boot, reset, boot, reset,boot

I've looked up the model X51 R2, there are various configurations, if you could tell me more about yours I could help more, what mobo, how much ram etc

However in the mean time you could try the following if you could confidently open and remove the ram sticks.

1. Turn off and remove power cable.
2. Open case and identify where your ram is.
3. On the motherboard beside the ram slots there should be (although not always) numbers that indicate what order the rams slots are in, if not, remember what order they are in (or take pictures). Usually the slot furtherest away from the cpu is the first slot. Or refer to your mobos manual if you still have it.
4. Remove the all the ram.
5. Take one stick a put it in the first slot, sometimes called slot 1, sometimes 0.
6. Try to boot.
7. If you still get the error you may have found the dud stick.
8. Power off the pc remove power cable.
9. Remove the stick.
10. Put in the other stick.
11. Power on.

One of many things can happen now;

It works, in which case you have the bad stick in your hand

It doesn't work, both sticks somehow died at the same time (extremely unlikely), OR your ram slot is damaged.

Let me know how you get on.