is there anyway i can restrict my exchange users from clearing out there deleted items folder on exchange server for certain period of time? thanks

you can let them empty it, but retain deleted items http://technet.microsoft.com/en-us/library/bb125266(EXCHG.80).aspx, however they can get around this with a shift+del, so i'd journal the mailbox(es) in question. http://technet.microsoft.com/en-us/magazine/cc160869.aspx

Utilize a third party archiving tool, or (if Exchange 2007) setup the Deleted Items containter as a Managed Folder and Journal content to a separate mailbox. The latter option isn't my preference, but it gets the job done. The separate mailbox may get very large and require automatic maintenance policies set as well (aging), and you need to consider company policies for harvesting the email from the users' accounts. Jeremy