Computer cannot connect to the internet

I recently got high speed internet through CenturyLink, and it was working great, but a few days ago my computer suddenly lost the connection. This has happened once or twice before, but restarting my computer or unplugging the modem for a little while solved the problem. Now my computer doesn't seem to be registering a connection to the modem. Xbox Live is working perfectly, so the problem seems to be with my computer. I also tried the ethernet cord I use for my Xbox with my computer, so I don't think it's a problem with the cord.

I'm now using my dial-up connection. I've been searching for possible solutions but I just don't understand what the problem is. I believe my network adapter is Realtek Virtual Adapter but it says it's working properly. In my device manager, the only problem is there is an exclamation point next to Audio Device on High Definition Audio Bus, but that probably has nothing to do with my internet (and my audio is working). Here is my information:

System:
Microsoft Windows XP
Professional
Version 2002
Service Pack 3

Computer:
AMD Phenom(tm) II X4 945

Network Adapters:
Direct Parallel
RAS Async Adapter
Realtek RTL8168/8111/8112/ PCI-E Gigabit Ethernet NIC - Packet Scheduler Miniport
Realtek Virtual Adapter
WAN Miniport (IP)
WAN Miniport (IP) - Packet Scheduler Miniport
WAN Miniport (L2TP)
WAN Miniport (PPPOE)
WAN Miniport (PPTP)

When I got disconnected, my high speed connection was no longer listed under network connections. While looking through network adapter properties and following some suggestions from the internet, suddenly an LAN connection popped up with an x saying it was disconnected, and I'm not sure what I did, if anything. It says "Local Area Connection 2" and I can't seem to make it work either. I don't remember if it's the same one as before, and since it says "2" it seems new? I think Realtek Virtual Adapter was missing from the device manager list while I was first poking around, and popped up at the same time as this second connection.

Thank you for your help.