Can someone ((help\w this problem please?))?

Greetings, several years ago my granddaughter(who now lives in South Caroline) built me a computer. The Motherboard is a MSI, CPU is 2.0, the original Hard Drive was a Western Digital Seagate 600, then she added (2) more 160 HD's (?) I forgot the name of the hard drives. later, she added an ATI\w DVI. finally she added a CD +DvD both reads & writes CD's & DvD's. Everything in this 1st build computer WORKS ((great!)) but there's a conflict somewhere. When I log on I must press F1, or I can't get to the WindowsXP Main screen. Is there anyway to correct this problem? Also when I try to log OFF I get a screen that says "installing 1 of 3 installments" which seems to never install, but continues to run for ever until I un-plug the system. HELP please. I don't want to throw the system away UNTIL I find out what went wrong.