Where R Outlook Express Newsgroup Stored?

good news
C:\WINDOWS\Application Data\Identities\{xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}\Microsoft\Outlook Express is where they are stored

bad news
each newsgroup is a file such as 3bconfig.dbx referencing the 3bconfig newsgroup

good news
a .dbx file is only created if you actually double clicked that newsgroup to catch up on the messages

so: the problem isn't really with the subscribed newsgroups unless you 'opened' a lot of them

you say it freezes
is this when you a) go to news and try to open it, or b) right at start up?

if it's a) - go to file in the main menu bar and select 'work offline', you should be able to click on news and unsubscribe (as rockn suggested) - or even go to tools, aco****s, and delete the news account, then recreate it later

if it's b) - i have no idea, could probably find the newsgroup account in the registry somewhere and delete it - someplace like here - do a registry search for news:
HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\00000009

always do a registry back up before changing anything