XP blue screen when trying to boot up

Hello,

Hi everyone I'm stuck! I was was recently given a second hand Benq laptop running Windows XP. I've had many e-mails over the past few days and when I came to boot up this morning I get as far as choosing the user i.e me then all I get is a blue screen. I've since downloaded a virsus software which detected a Trojan virus which has been cleaned. However No matter what I've tried I still cannot open Windows. Any suggestions?

Cheers