system
1
Hi,
I am an Avast!4 Home Edition user.
I converted my hard disk from FAT32 partition to NTFS partition…
After reboot, Avast!4 Resident Protection closed. It appeared a window saying to update my Avast! Home Edition to Professional Edition…
I checked Avast! configuration and I manually reactivated Resident Protection.
After, I run Avast! and I notified the Registration number disappeared…So, I refilled it in the specific field and finally it’s all ok now! ;D
Is it a little bug? 
Bye from Italy
Vlk
2
Hey, stop cracking our software…! ;D ;D ;D
Well, you figured it out - the registration key is stored somewhere on the disk, and it got lost when you changed the disk’s file system… 
Mere re-entering of the key should solve the issue.
Vlk