How secure is your computer after a threat is removed?

this was the infection on my PC:  EMAILNOTIFIERSETUP[1].EXE Pua.Xacti  Does anyone know what this is and tell me more information on this.

Thats not malware its for a unwanted program, its not malicious in any way. 

As Rakanisheu noted, it is not actually malware, but it MIGHT be 'annoyware'.  Here is a little info about this general type of item:
 
What you are seeing and describing sounds like it may be what we on the Community refer to as a PUA. (Potentially Unwanted Application)These are very annoying at best in that they cause pop-us, redirect your browser home page, and other behavior that may slow down the computer and direct ads your way, but they are not actually doing anything bad like damaging files or stealing information. Often they are installed intentionally by you the user as browser add-ons for various tasks such as quick search tools.. but they also come with the result of added annoying pop-ups and ads. Other times they 'piggy back' with other software that you installed, or try to 'sneak' onto your system entirely.
 
WSA does detect and remove many PUA's, and more are being added, but WSA does not detect all of them. A simple browser add-on with PUA behavior that is easy to identify and easy to remove is not likely to be detected and removed by WSA. Those that are intentionally difficult to locate and remove are. Please see THIS LINK for more information regarding Webroot's stance on these annoying programs.
 
For those that are not detected by WSA, please see this KB Article. It has some easy to follow directions on locating and removing PUA's. You may also want to submit a Trouble Ticket, especially if you cannot remove it easily from the directions in the KB Article.
 
For those that ARE detected by WSA, but cannot be removed automatically, you can submit a Trouble Ticket.  Webroot Support will help you get these annoying 'crapware' off your computer at no extra charge, and the additional examples may help to better automatic removal of that particular PUA for all users in the future.
 
To make sure that your WSA is checking for PUA's with the best proficiently, it sometimes helps to reset the PUA detection within WSA's settings. For PUA's that had previously been scanned and determined to be OK, but have since been added to detection/removal, you may want to complete the following steps:
 

• Open Webroot SecureAnywhere
• Click on ‘Advanced Settings’ from the top right
• Select ‘Scan Settings’ from the left side
• Unselect the option “Detect Potentially Unwanted Applications”
• Click on the Save button (you may have to enter in a CAPTCHA)
• Reselect the option to “Detect Potentially Unwanted Applications”
• Click on the Save button
• Run another scan with Webroot and remove any items that get detected.

To help avoid PUA's in the future, remember to read all of the information when installing or updating software (Adobe downloads often have those "extra special offers"attached... PUA'S!: often the PUA included will be mentioned, and you can opt out of installing it.  Those check boxes you see? Usually only one of them is for the User Agreement of the software you want, the others are for the junk you don't.
 
 I hope this helps you both understand,

Thanks everyone your information will help me out.

You are most welcome!
 
Please come back any time you have a question or problem.  We may be mostly volunteers, but we really have some good people and love helping out when we can.

So how do I really know if a threat has been removed from my PC after a scan?