I had Vista installed on

Question

I had Vista installed on my computer which was leant to my ex, needless to say she installed a windows password which after getting the laptop back i was not able to crack. So i tried to bypass by reinstalling windows Xp proffessional however now all that comes up is a blue screen telling me a problem has been detected and to check my harddrive for errors. my laptop is a Acer Aspire 5103WLMI