My PC is installed with softwares like Visual Studio 2010, SQL Server 2008 etc. I need these softwares very rarely, for example once in a month.
How can I improve my PC performance by stopping unwanted service, because some components of SQL is designed to run always.
I cannot uninstall and the re-install these softwares because it is very time consuming. How can I stop all services related with this kind of softwares
There's no need. Services that aren't being used only affect system startup, and most of these services start on demand anyway. Basically, there's nothing you need to do. The services are already designed not to impact performance when they aren't being used.
You'll notice that the people who claim that disabling unnecessary services improves system performance never provide benchmarks to backup their claims. There's a reason for that.
If someone tries to talk you into disabling a bunch of other services, ask them what you stand to gain. I’ll bet they can’t tell you. - Ed Bott
This is an example of people repeating incantations that worked for others in the distance past without understanding why it was needed and therefore when it isn't needed. It's cargo cult IT.
I assume you use windows. Press window key to open start menu. Then search for "services". Now in the opened list look for services you don't need and turn them off. Disabling unwanted services can free up some memory space.
