Vista Fix for Drive size for backup

About a year ago Bill put an advice video on how to limit the size of backup that vista takes. I have a Lenovo with a Q drive that is for Backup. I set it at 5 gb. However I need 10gb. This puter is running very slow it has taken me over 15 minutes to get this much typed in. Bill used Vssadmin resize Shadowstorage. I need to get this again it worked the first time now it wont I must have copied it wrong. Thank you James Casper Ynotrepsac@aol.com