"I've read that your PC will start up faster by deleting applications from the start up menu."
You may be confused about that. Deleting items from the start up (menu), has no effect on the start up speed.
However the programs in the start up file, are the programs that start when the computer is started.
To see what programs are starting up at boot, go here:
Start/Run/type msconfig/OK. When that loads, select the start up tab to see what is running at start up.
Best of Luck