WoWoWo! You can be on WIFI, but that doesn't mean anything. Contact your ISP. If it is your WIFI device, then read the INSTRUCTIONS again! If it didn't come with any instructions, then good luck with that! Or, if it is used, then it is up to you to configure it, as each ISP has different options. Once again, good luck with that! If it used to work, but now it doesn't, plug in your rig into the ISP modem with the same cable as the wifi device, and see if you can browse (pull and IP address) from that. If you still cant' check to make certain that you are not a static IP. Put in a DNS of 188.8.131.52 and hope! If that doesn't work, contact the last person who sold you the PC (or loaned it to you), and they will go ahead and help you!
I hope I have covered just about every scenario!