Mysql Problem and i spose phpmyadmin

well, yesterday i was trying to make a database on my computer with phpmyadmin. It worked the day before and all the other times but now it wont let me, access is denied. I just get an error (1045 Access denied for user root@localhost using password :no)so basically wot do i do? i hadnt touched anything, it just stopped working. i cant think of anything that could have happened besides that my IP had chnged from the last time i used it.i cant use phpmyadmin or the command line.oh and im using xampp by the way, and its on my jumpdrive using portable apps.anyone know how to fix it? my best friend would know wot to do but he conveniently went to sydney the day before :l