Q: getting error 3253 while downloading ios 6.1.3 on windows 7.

"Error 3000" through "3999"

Alerts with codes in the 3000 range generally mean that iTunes cannot contact the gs.apple.com server on ports 80 or 443. This may be because out-of-date or incorrectly configured security or firewall software is interfering, or due to your Internet proxy settings. If you are using a proxy, try removing the proxy settings, or using a known-good network. If that does not resolve the issue, follow iTunes for Windows: Troubleshooting security software issues.

Hope it helps

I had this same issue and it ended up being a firewall on my router. Please look at your router firewall settings!