Win Defrag is a fake system optimization tool that spreads on computers through Trojans. It's a creation of cyber criminals who are looking for easy ways to earn lots of money. In this case they offer purchasing a program which is completely useless. They attempt to prove that Win Defrag is a system defragmenter and offer purchasing it in order to fix your system errors.
The program will not allow running most of the programs by terminating them right when you try to run them and instead you will receive a message stating that you detected a hard drive problem or that Windows cannot find the program you want to open. You should know that these messages are fake and they are only displayed in order to mislead you into thinking your system has been infected. You will see that after several tries you will manage to launch the program. However, it's a very annoying consequence.
Another thing to be mentioned is tons of security notifications that will be displayed while Win Defrag is running. These messages state that your computer is badly infected and it pose risk to your private data. All this kind of messages eventually will lead to promotion of Win Defrag as the only purpose of its creators is to gain money from as many computer users as possible.
You are strongly advised to get rid of Win Defrag as soon as you notice its activity on your computer. Run a full system scan with a reputable antispyware soft and eliminate it quickly and easily.