BAD_POOL_CALLER Someone can help me please?

Hi there! first, sorry about my english

I have the computer from a friend, and I have the next problem:

- The computer reboot always, when windows try to start (Just when the mouse appear in the screen more or less). This start to happend without any reason in external damage.
- I dont know if its a Virus, or its a hardware problem, I can not start windows, so I dont know how to check the computer. (I try in safe mode, but the same thing happened, reboot at start)
- I have windows XP in a CD, and when I try to repair it, its show this: "Windows must shut down to prevent damage(blue screen)"
- In the BIOS, I can not find the option for change from IDE/SATA or SATA/IDE, I think its a simple BIOS, so I can not.

1- ¿How I can solutionated this without lost any info inside the laptop please?
2- ¿How I could change IDE/SATA if I can not see it on the BIOS?
3- If its a virus, ¿How I can try to delete it, if I can not entry in Windows?
4- ¿If I install other windows, could I keep the info inside the HD? (Well.. when I try to run my Windows CD, show me: "Windows must shut down to prevent damage(blue screen)" but well, I dont know what to do..)

The only thing theat I need its to safe the info inside the laptop, I dont care what I need to do, I do it if I dont lost anything hehe.
I have a Macbook as well, I dont know if can be helpful for try to repair it.
I hope that someone can help me, I will be very grateful with him. Thank you so much!