in my experience in computing i found that there are viruses (in this case malware) that make your system show a fake windos error prompt (usually telling you that there is spyware or viruses in the computer although there isn't) and that you need to download the offered software (in which i find suspicous windows doesn't just offer free software through an error prompt for free) and i also found out that if you try to click don't install is triggers virus installation and if you click the X in the corner it will also trigger a virus installation

it downloads rogue software that automatically installs itself into your comuter (it is malware that disquises itself as a spyware protection program, virus protection program, or a registry cleaner) and acts as it is scanning your system and shows fake threats and says that if you want to get rid of them you have to buy there product.

how do you cancell these you whenever you encounter a promt that seems like it will download one

I believe I encountered a rogue software last week. Received a pop up for a trojan virus. Ran my AVG software and thought I repaired system. Now windows close on their own. I cannot update windows or any antivirus. I have run AVG, Avast, SuperAntiSpyware and yahoo antivirus….nothing is found. I can not do a system restore, nor can I start up in safe mode (F8). I am running Windows XP. Can someone tell me where to turn next