Problem connecting USB

Hi All!,
I have a problem with my USB. The issue is that when i connect my pen drive to my compaq presario, Win XP PRO SP2 don’t recognize it as connected. But when I reset the Laptop with the Pen Drive connected, XP see it. This problem occurr with all devices that I connect to the USB like my Sony MP3.

I don’t know what is happening, I hope you can help me.

Thanks in advance.

Solearg.