32 bits is like a 32 lane highway, while 64 bits is like a 64 lane = can carry more traffic. Like David notes, you probably don't have a problem, with viruses or such.
You may have a problem with such common nuisance as your HDD fragged > defrag it. Or some mysterious program using CPU. Check the use of your CPU > Ctrl+Alt+Del > Task Manager, there may be someone running all too high.