ASSUMING you are using Outlook or Outlook Express as a mail server, go to tools accounts and make sure your ISP is setup correctly. If the repairman re-installed your XP, then most of those settings are gone. You may need to re-establish your dial up as you did the first time around. The network between the two is most likely Ethernet, which would be different from a dial up modem. Look also at the connection tab under the browser to see if it is set to always try using the LAN (your network) as opposed to your dial-up (modem). That is the best I can interpret your post.
I have just got my laptop back from repairer and tried to network it with my desktop. Both have XP. I followed all the instructions as far as I was able to understand. Managed to drag a file across from one to the other. Want to keep the dial up on Desk Top and the connection showed on Task bar on Laptop that it was connected, but I couldn't download or send any email. have I missed something ?

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