UV83GR-J48Q62-4W3ZYA I need to activate it i had to restore my computer to new and it deleted my avast.

once istalled Avast Free, follow easy instructions to activate free. that's all you need to do

http://www.filehippo.com/download_avast_antivirus/ Freeware.

Find clean pc and a usb stick. THEN GO HERE:
WWW.MALWAREBYTES.ORG AND DOWNLOAD THE FREE VERSION. SAVE TO DESKTOP. IT WILL SHOW UP AS MBAM.exe. BEFORE DOING INSTALLATION,turn off system restore and RENAME mbam.exe TO winlogon.exe
INSTALL, UPDATE, AND RUN FULL SCAN. DELETE EVERYTHING IT CATCHES AND REBOOT.turn system restore back on and create new restore point.
THEN DOWNLOAD NEW ANTIVIRUS. iF YOU CAN'T AFFORD TO BUY YOU CAN USE AVAST FREE VERSION AND ZONE ALARM FIREWALL FREE. OR YOU CAN SURVIVE FOR MONTHS ON FREE TRIALS OF KASPERSKY, WEBROOT, BITDEFENDER, AVG, AVAST, ETC, ETC.
GOOD LUCK AND IF I'VE HELPED PLEASE CONSIDER GIVING ME A GOOD RATING.
THANKS AND GOOD LUCK.

First.. install a different antivirus program while you are fixing this installation. Try microsoft security essentials or AVG.
Then.
Check your program files folder for any mention of Avast, and delete it.
Run a search for avast and delete anything you find.
Download a registry cleaner, I use CC Cleaner.
Run the cleaner and remove all the files it finds, run the registry cleaner and let it delete all the problems it finds .
IF you want to try with avast again, uninstall the other antivirus program you may have installed. then try with the Avast again

Disable System Restore. Scan your computer with the free version of Malwarebytes' Anti-Malware.
http://malwarebytes.org/
If you don't have an Anti-Virus program, download Avast and scan.
http://www.avast.com/
If both scans don't detect anything, do this..
Ctrl-Alt-Del > Processes - End the following processes in order:
dxdlg.exe
wscript.exe
Start > Run > regedit - Open the following key:
HKEY_LOCAL_MACHINE\SOFTWARE\ Microsoft\Windows NT\CurrentVersion\Winlogon
In the right hand pane, select Userinit and delete everything except C:\windows\system32\ userinit.exe

Make sure the processes wscript.exe and dxdlg.exe are not running.

Delete the following files
C:\Windows\System32\dxdlg.exe
C:\Windows\System32\boot.vbs
In your Windows drive, search for boot.vbs and delete all of them.
In your Windows drive, search for kinza.exe and delete all of them.
Enable System Restore.
Restart your computer.

Avaste is good but I suggest using another
program for your problem. Actually 2.

SUPERANTISPYWARE (free)
http://www.superantispyware.com/download.html

PANDA ACTIVE SCAN ONLINE (free)
http://www.pandasecurity.com/homeusers/solutions/activescan/

Also, when infected, I suggest running in safe
mode. Also delete (disable) Restore Point as
the infection could be in a backup set. Be sure
to enable it when done.

Hope this helps.

Multiple anti-virus programs on a computer conflict with each other, as well as installation may fail when trying to install one Anti-virus program when another one is still on the computer.

Download Avast
Disable your internet connection, or unplug the ethernet cable
Uninstall McAfee
Install Avast
Hook your internet back up
Use your reg key and update Avast.

You just don't want an unsecured computer with an active internet connection even during the short period of time between uninstalling the old one and installing the new one