Blowing running lights fuse
 

Good morning.....JUst went to get a sticker for my 95 pickup xe and failed due to no runing lights. Rreplaced the fuse and as soon as I turn on the lights it blows again. THe only thing I can think of is I just replaced the radio. Would that have anything at all to do with this? What would be the first thing to check?
Thanks in advance for your help...