This fix is for Windows XP with Service Pack 2 installed - Previous versions are not affected.

With the arrival of Service Pack 2, a lot of users might encounter problems while downloading torrents or running other P2P software. In XP SP2 there are only 10 concurrent TCP connection attempts possible, while in XP SP1 it was not limited. The limit is hard coded in the TCPIP.SYS and changing a registry key will have no effect at all.

A symptom could be your downloads freezing from time to time while Protowall is still logging IP’s.

But how do I find out if I’m affected by this?

Go to Start – Control Panel – Administration Management – Event Viewer - System
Look for an entry like this:

EventID 4226: TCP/IP has reached the security limit imposed on the number of concurrent TCP connect attempts

If yes, you've reached at least once the limit.

You can read more about it here and download a fix. Take some time to read the instructions and make a backup of your existing TCPIP.SYS just in case something goes wrong.

Faq: http://www.lvllord.de/?lang=en&url=4226patch/faq
Instructions on how to use: http://www.lvllord.de/?lang=en&url=tools#4226patch
Fix: http://www.lvllord.de/?lang=en&url=news and click on the download link.

Credits :
This sticky has been made from AndyZan's original post and hard work located here : http://www.bluetack.co.uk/forums/index.php?showtopic=6564

Kim