searching online, i found a possible solution.

try this:

Re: "SNMaster.idx Database is missing Please restore this file"

I was having the same problem after i attempted to install AOL 9.1 on Vista. I posted this fix on an aol forum as well. Locate the appdata.ini which should be located in c:\program files\AOL 9.1 . Open the appdata.ini and modify the "Folder=" section like below..

Double check to make sure that the snmaster.idx file actually resides in C:\Windows\All Users\Application Data\AOL\Ca_AOL 9.1 . I'm assuming the problem exists because there is no absolute path by default in this appdata.ini file.

[appdata]
Folder=C:\Windows\All Users\Application Data\AOL\Ca_AOL 9.1
GUID=d2daa36-8ec8-4e9e-85f5-c1328ad905a0
Common=C:\Windows\All Users\Application Data

Browse to C:\Program Files\AOL 9.1\ and double click on aol.exe. It should start just fine.

or this:

Re: "SNMaster.idx Database is missing Please restore this file"

Folder=C:\Windows\All Users\Application Data\AOL\C_AOL 9.1

Simply change your reference in appdata.ini to the above and all is well! It's not CA_AOL 9.1 but C_AOL 9.1

It's a simply path direction reference mistake by AOL

here is the link:

http://text.broadbandreports.com/forum/r18503301-SNMasteridx-Database-is-missing-Please-restore-this-file