What's a good spyware detection guide?

Spyware detection help and guide please. It is now very very pathetic conditon to use intenet safe. There are number of thousands of viruses, spyware, horses , trojons are now spreaded all over the internet. Use internet safe is now a day dream. So it is very essential to use a good, dignified spyware detection and prevention system in our computers if we use in on net. And the first thing is first. I do not prefer to spend some money on it. Here the problem is this, it is very hard now to select out of a lot of available free to use spyware detection softwares. Because waht I fear is that spyware detection software itself may bring some virus or spyware in my pc. So here adviced are welcome from those who already using some good quality spyware detection software.