Need help urgently, discovered a trojan virus

hi, i am having trouble with my Samsung NP- R519 laptop, i have recently scanned my computer and i have discovered a trojan virus on the hdd, got it from downloading a stupid keygen, (wont be doin that again), so to remove it i want to restore to the laptop to its original factory settings, as the virus is slowing down my laptop but i do not how to, so i was wondering if somebody could help me?

my OS is WINDOWS 7 Professional, which came pre installed when i got it.
if anyone has any information can you kindly help me please thank you.

thank you for your help, but would i need to make a windows 7 installation cd, if so how would i go about doing this?

thank you again, but i was wondering, when i do the samsung recovery, will i have Microsoft Office 2007 still installed because the laptop also came pre installed with that.

similarly will the windows 7 os still be installed?

errore13 said:

similarly will the windows 7 os still be installed?

The OS will still be there, but if you do a full recovery you will lose everything including all user data and installed applications

When you do a factory recovery, your computer will be restored to exactly what it was when you unboxed it. And, before you ask, back up any critical user data, theres no guarantee it'll be usable after the restore. Quarantine that data to an external drive, then scan it thoroughly before using it.

If your AV, Malwarebytes and one of the bootable AV scans do not find further infection, you can wait to see if infection resurfaces: http://www.techmixer.com/free-bootab...download-list/

The problem with factory recovery is that it doesn't wipe the HD of infected code which can live on under a simple format. So if an infection plagues your install it is best to wipe the HD to clean reinstall with Recovery Disks or Win7 installer.

If you purchased the Office Trial version pre-installed on the computer, be sure to back up the Product key which was given you. If you don't have it, audit it from the HD along with all other installed Product Keys using Belarc Advisor. Belarc Advisor - Free software downloads and software reviews - CNET Download.com

I would not select to have Recovery save your data as you want a formatted reinstall at the least. Even better would be to wipe the HD of all infected code and reinstall using Recovery Disks or Win7 Installation DVD. Remove your data to quarantine on DVD, external or flash stick to scan it with AV and Malwarebytes, or sacrifice it rather than risk reimporting infection..

SSD / HDD : Optimize for Windows Reinstallation
re-install windows 7