If you do not want any such situations in your computer then you can visit this website, to get one shareware software for Free daily. Although there are many websites that do offer paid software as freeware, but they are usually illegal and are known as warez. But at Giveawayoftheday.com they provide legal free license with every download, with which you can use the software indefinitely !
And not only a freeware software but also they provide one free paid game to download daily ! [Game.Giveawayoftheday.Com]
The only problem with the products from this site is that, after a system format the license no more holds valid, and you'll lose the product, but the selected products by them are usually very different and creative which you can search on Internet sometime later and download similar freeware programs :)