I need help pleasssssssseeeeeeeeeeeeee

alright
i custom built my computer recently, and installed windows XP home edition on it
it worked fine for quite a time, and suddenly, when the windows starts and when the sign "welcome" pops on the screen, it takes like more than 10 times longer for it to load than it used to
any ideas what's wrong?

im guessing memory but thats just out of the blue


any posts would be great

thanks