Hey Lancey,
This is an employee of a major ISP out there (company name withheld, as to not to tarnish the company name if this doesn't work..hehe), and we've got internal tools galore that explain SEVERAL possible options for you. I'm going to paste a list of possible causes and abreviated fixes for you, and you can go through them one-by-one. Note, that these ARE for ALL versions of Windows, and some of these fixes won't apply. WinXP is so new, our internal knowlegebase doesn't have the updated fixes for XP yet. Yet these may still apply to you in one way or another.
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1. Error 720: Could Not Negotiate a Compatible Set of Network Protocols / Extract System Files
If you receive the error message: "Error 720: Could not negotiate a compatible set of network protocols," it may be because the System File Protection is disabled and the vip, vtcp, vnbt, vdhcp, and vtdi 386 files are deleted or renamed. Resolve the error by manually extracting the files. ...
2. Error 720: Dial-Up Networking could not negotiate (Win 95) / Manually configure the computer to connect to the Internet
3. Error 720: Could not negotiate a compatible set of network protocols (Win 95/98) / Create a new Connectiod
4. Error 720: Could not negotiate a compatible set of network protocols (Win 95/98) / Reinstall Network Components
5. Error 720: Could not negotiate a compatible set of network protocols... / Uninstall and reinstall TCP/IP
6. Error 720: Could not negotiate a compatible set of network protocols... / Check for line noise
7. Error 720: Dial-Up Networking could not negotiate... / Make sure the correct Network components are installed
If the TCP/IP protocol is not installed in the Network section of the Control Panel you will not be able to connect to the Internet. Check to make sure the correct Network components are installed and install any missing components.
8. Error 720: Could not negotiate a compatible set of network protocols... / Disable Global DNS
9. Error 720: Could not negotiate a compatible set of network protocols... / Enter Modem Initialization String
10. Error 720: Could not negotiate a compatible set of network protocols... / Unbind unneeded protocols
11. Error 720: Could not negotiate a compatible set of network protocols... / Make sure TCP/IP is installed
12. Error 720: Could not negotiate a compatible set of network protocols... / Check modem speed
13. Error 720: Could not negotiate a compatible set of network protocols... / Check the Network Bindings
14. Error 720: No PPP protocols configured / TCP/IP is not bound to the Dial-Up Adapter
If you receive the error message: "Error 720: No PPP protocols configure," it may be because TCP/IP is not bound to the Dial-Up Adapter. Resolve the error by installing TCP/IP.
15. Error 720: No PPP control protocols configured / Install NetBios Interface service
Error 720 may be resolved by installing the NetBios Interface service in the Servers tab of the Network Control Panel.
16. Error 720: Dial-Up Networking could not negotiate... / Make sure Global DNS is not enabled
17. Error 720: Dial-Up Networking could not negotiate... / Check the Server Types settings
Error 720 may be resolved by setting the Type of Dial-Up Server to TCP/IP in the Server Type properties of your <ISP> Dial-Up Networking connection.
18. Error 720: Dial-Up Networking could not negotiate... / Reboot the computer
Error 720 can be resolved by restarting the computer in order to reset the modem.
19. Error 720: Could not negotiate a compatible set of network protocols... / Use the correct Dial-Up server type
20. Error 720: Dial-Up Networking could not negotiate... / Make sure the modem speed is set correctly
21. Error 720: Dial-Up Networking could not negotiate... / Create a new connection
Error 720 may be resolved by creating a new <ISP> Dial-Up Networking connection.
22. Error 720: Dial-Up Networking could not negotiate... / Restart the computer
23. Error 720: Could not negotiate a compatible set of network protocols... / Reboot the computer
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One other possibility would be to reset your TCP/IP registry settings to default. Usually this would involve removing and re-installing TCP/IP in previous versions of Windows, but since XP considers it a 'core component', it won't allow you to remove or re-install it. However, you can zap the registry keys back to default. Here's the instructions on how to do it:
netsh int ip reset resetlog.txt
It will go through and reset your TCP/IP settings back to default, and keeps a log in resetlog.txt of what actions it performed on what reg keys.
If all else fails, call Microsoft?? =)
