My name is Prateek and I work for the Social Media and Community Team at Dell.
As mentioned your system is been infected by virus and in order to remove it you have bought a anti-spyware software and you are not able to install it .so these are a couple of steps which you can follow to fix the problem
1) Try to reboot the computer in safe mode and in order to do so you have to press F8 after pressing the start button.
2) You will get advanced boot option and you have to select Safe Mode with Networking, select that option and press enter.
3) After that open internet explorer and we have to install malware bytes that will help us in removing infected files , link is attached to install malware bytes anti-spyware software Malwarebytes : Malwarebytes Anti-Malware PRO removes malware including viruses, spyware, worms and trojans, plus it protects your computer
4) Moreover you can install your own software as well in safe mode , try to open following link STOPzilla - Award-winning Virus Remover
and then click on virus and malware remover icon (green tab) and click
5) You can also use Download Trojan Remover
and click on download 1 and install it and then run it after that .
6) After that we have to restart the computer back in the normal mode and then we have to run this software.
7) Let the scan complete and it will show you infected files and you will get a prompt to delete infected files , try to run both of them one by one ,
8) Once we are done with this then restart your computer ,I hope that will fix your issue