Changing a Registered Name

Dear,
I have a few questions hope you will reply soon
1) How to change the Registered name and organisations name of a PC.
2)I installed a 256mb ram, at shows me that it is active but I want to make sure that RAM is working how?
3)I recently encountered a problem while installing a OS (” A problem has to prevent damage to your computer…….0X0000008E,0XC000001D,0X805813BC,0XF96AFB04,0X00000000″) this is the error showing on the screen?

Thanks in Advance