I have a gateway computer I'm upgrading . I put more memory in 198 mb to 512 md. I also put a hard drive in 20 gb to a 40 gb. and i am tring to put win xp pro on from me. sometimes I get a error mes that saysNTLDR is missing and some times i it shuts the windows xp install downand says technecial stop:0x00000050 (0xFE3021AC, 0X00000000,0X00000000,0X00000000. HELP ME