Siamak - Here are the things I would try in order to resolve this issue:
- If you have another iPod/iPhone sync cable, try to do the restore using a different cable to remove the cable as the source of the issue.
- In Windows, create a temporary user account with administrative rights. After you create the account, login using that account and try to restore your iPod. This should eliminate any corruption issues in regard to iTunes, the IPSW file and your primary account.
- Make sure you have totally disabled your Windows firewall. Here is an article that explains how to do that http://kb.linksys.com/Linksys/ukp.aspx?pid=104&vw=1&articleid=27292
- Connect to a public wireless network (like at a starbucks) and try to download the IPSW and restore using that connection.
- Change the physical USB port you are using to do the restore. Many older desktops (although I think you said back on your post on SU that you were using a Windows 8 laptop) will have USB 1.1 ports, which can cause issues with restoring your iPod.
- Find a another computer that you can download and install iTunes on and try to restore using that computer. I would reccomend not trying this from your own home if possible (ask a friend) because the error you are getting is due to not being able to contact the iTunes update servers (for whatever reason).
The KB support article from apple clearly states the following:
Errors 1639, 3000-3020, and 3100-3999 (with the exception of 3194) are
sometimes caused by your network settings. If your computer uses a
managed network, refer to your network administrator. Proxies,
firewalls, and other network security measures can cause these errors.
If necessary, find a different network connection to restore the
device. For example, if you're restoring at work, try to restore at
home or on a friend's computer and network.
I know you had said previously that you had tried the suggested fixes in the KB article, just want to be sure you attempted this part of the article
Address TCP/IP filtering, firewall, or security software
If you have TCP/IP filtering, firewall, or security software installed on your
computer, follow these steps.
Follow these steps to configure or temporarily uninstall your security
software. Bypass your Internet router. Some routers might block iTunes
from accessing the update server. If you're using a router that isn't
manufactured by Apple, try these steps.
Disconnect from your wired or wireless router.
Use an Ethernet cable to connect directly to your modem.
Restart your computer and modem. Contact your Internet service provider for
instructions on using your modem.
Be sure you have a
working Internet connection by visiting www.apple.com.
See these steps
for help or contact your Internet service provider. If your Internet
connection is working, try to update or restore your iOS device again.
Hopefully one of those suggestions will allow you to restore your iPod.