all these simultaneous actions requires your windows system to open many outbound ports and bind them i.e in simpler words, windows allows many connections to different applications at the same time.
But have you ever realized that Windows by default only allows 10 outbound connection attempts at a time?
This can restrict bittorrent applications from performing at full speeds. A simple patching utility can fix the problem and speed up your BitTorrent downloads.
Microsoft first introduced these limits into Windows to prevent viruses and worms from spreading—because they try and connect to thousands of addresses at a time looking for security holes. What ended up happening instead is a restriction on your BitTorrent downloads, especially from busy torrents where your machine may need to connect to plenty of other systems at once.
This utility patches a critical system file so readers must proceed with caution! it can be downloaded for free from here.
Half-open limit fix is a program designed to change the maximum number of concurrent half-open outbound TCP connections (connection attempts) in the Windows system file tcpip.sys. as the developers suggest, for majority of Internet users, changing the limit to 100 will be more than sufficient.
For Vista and Windows 7 users: Maybe sometime, after updating Windows or SP installation on a desktop will appear watermarks "Test mode". They can appear because in all versions of Vista and Windows 7, except Vista without SP(x86), there is the obligatory drivers signature check, and the tcpip.sys file sign with test signature after patching. Most likely, to make it disappear will be necessary simply once again to patch tcpip.sys.