Thunderbird extremely slow in Win2000

I was running 0.8 and recently downloaded 1.0.  They both run extremely 
slow on my Win2000 machine.  It takes forever to mark a message as 
"read" (settings are 0 seconds to mark as read) and to delete a message.

Does anyone know of a way to fix this.  It's quite annoying when trying 
to go through a ton of emails.

Thanks in advance.

b.