Hmm... this can be caused by a lot of things. Internet explorer likes to give you that generic error message. :(
Does this happen with every website, or only with certain websites or when you try to perform certain actions, such as a "secure" login?
A few ideas:
Try a different internet browser, such as
Mozilla. Maybe this will help the problem.
Although it is very unlikely this could be the cause of your problem, you might want to check your DNS (Domain Name Server) settings for your ISP. These settings tell your computer what servers to look for to get the correct IP addresses for doman names (such as yahoo.com). You should be able to find the correct DNS servers on walmart's website.
Note that these settings are usually automatically detected. As walmart's isp was certainly designed for windows, then the windows dial-up thing should auto-detect the DNS... If you can get to ANY websites, then this is probably not the problem.
~psi42