Backup Problems - DISK A:

Hy Guys!
I`m having a BIG problem!

This is the way i`m following:

All Tasks - Restore Database - From Device - Select Devices - Add - ...

Error!

Take a look in this popup:

EVENT ID: 26

DESCRIPTION:
Application Popup: sqlserver.exe - No Disk: There is no disk in the drive. Please insert a disk into drive A:

Thanx!You know sometimes Microsoft remembers the last time it opened Explorer, which may have been the 'A' drive, who knows. But have you tried putting a disk into 'A' drive just to get past the error?|||Yes I putted.
But, when i removed it..
The same problm...|||So what steps did you do:[list=1]
Put disk into 'A'
Go into Enterprise Manager and add a backup device
The new backup device you choose was on a drive other than 'A'
Close the Backup/Restore screen
Remove disk from 'A'
[/list=1]
Then go back into Back/Restore?|||I did exactly this. But the same problem.
----------------------
Now,
Take a look in this article:
http://support.microsoft.com/default.aspx?scid=KB;EN-US;q301077&

Microsoft tells to install W2K SP3. But it is already installed.

I can`t install the offered patch... It may trouble SP3 instalation...

What do You think?

Should I Install patch ? I need to restore a Database...

PS.: Doing this with T-SQL gives the same message...

This is a servetr that controls almost all bank transactions of BB the principal bak of Brazil.|||I don't want to make the call, but if I had clean backups of my databases, I would apply the patch. However I feel confident that given any situation I would be able to recover.
It is up to you. Not what you wanted to hear.|||heheh!

Not what I wanted to hear.
But, need to be done!

Really appreciate your help!

Thanx!