To safely upgrade to Windows 7, please follow the steps below to download the latest ESET product installer, uninstall your current ESET security product, upgrade your Microsoft operating system from Windows Vista to Windows 7 and then reinstall your ESET security product:

1. Download the latest version of ESET Smart Security before you uninstall your current version so you will not have to browse the Internet without Personal firewall protection. Click the link below that matches your system type (either 32-bit or 64-bit Windows) and save the installer to your Desktop:
   
   
   • 32-bit version of ESET Smart Security 4.2: http://download.eset.com/download/win/ess/ess_nt32_enu.msi
     
      
   • 64-bit version of ESET Smart Security 4.2: http://download.eset.com/download/win/ess/ess_nt64_enu.msi
   
   You will be prompted to enter your username and password to download your ESET installer file. Click here if you have lost or cannot remember your username or password. Note that running ESET Smart Security/ESET NOD32 Antivirus 3.0 and Windows 7 are not officially supported by ESET.
   

   

   
   Important! Do not attempt to run the installer yet. If you are prompted to click Run, instead choose Cancel. You'll need to do the installation after your upgrade to Windows 7 is complete.
   
    

2. When your installer file downloads, uninstall ESET Smart Security by clicking Start → All Programs → ESET → Uninstall. After you uninstall, you will need to restart your computer.
    
3. After restarting, confirm that you can see hidden files and folders by  clicking Start → Control Panel → Appearance and Personalizations → Show hidden files and folders under Folder Options and select the Show hidden files and folders option.
    
4. Click Start → My Computer. Navigate to and delete the following folders:
   
     C:\Program Files\ESET
     C:\Program Data\ESET
   
   If the above folders are not found, proceed to step 5.
    
5. Upgrade your operating system from Windows Vista to Windows 7 by following the instructions provided by Microsoft:
   
   Getting started with Windows 7
    
6. After you have successfully upgraded from Windows Vista to Windows 7 and have restarted your computer, navigate to your saved ess_nt32_enu.msi or ess_nt64_enu.msi installer on the Desktop and double-click it to open.
    
7. Click here for step-by-step instructions for installing ESET Smart Security. Please disregard the download instructions (as you already have the ess_nt32_enu.msi or ess_nt64_enu.msiinstaller on your Desktop) and start at the step labeled Installing ESET Smart Security 4.2. Click here for a tutorial video for installing ESET Smart Security. 

Related: 

I upgraded to Windows 7 and my Personal firewall stopped working. What do I do?

I lost my username and password

Installing ESET Smart Security (4.0)

How do I uninstall or re-install ESET Smart Security/ESET NOD32 Antivirus? (4.0)

Which version (32-bit or 64-bit) of ESET Smart Security or ESET NOD32 Antivirus should I download?

Microsoft Windows 7 Help & How-To