You Have to follow these some steps.
1. Install the latest version of firefox
2. Go to this link https://addons.mozilla.org/en-US/firefox/addon/13793/
and install add n edit cookies and restart the firefox
3. Open www.fileserve.com
4. Now on firefox click tools>cookie editor
5. Now in the top of cookie editor you will see a filter bar
6. Now in filter bar search fileserve
7. Now double click on the site that cookie name is PHPSESSID
8. Now copy the content and paste it there in content bar and save
10. Save it and refresh the page.
Sometimes it seems free account,refresh page or try again later to get premium account
If You Have Successfully Logged With This Cookie Don't Click On Logout.