I don't know how old the computer is, but it is possible that you have newer hardware than XP recognizes out of the box. If you look in the Device Manager as mentioned in a previous post, the network adapter would should up with a question mark if it is not recognized, the same would hold true for the memory stick reader.
If the device is recognized, but doesn't work, you might need to download the software for the adapter and let if manage it instead of windows. I have an Intel wireless card, and need to use their software to run it. Windows XP can manage the connection, but I never got it to work exactly right without using the manufacture's software, which also was much easier to use.
If you can provide the company name and model of the computer, it might be easier to nail down any issues.
Were you able to save off any data that wasn't backed up previously? I am assuming if you could get a command prompt you could have off data before the format.