Why?
I put $25 on my account and I forgot my security password and I can't purchase anything.
iPad
When you say your security password, do you mean the password for your Apple ID for purchases?
If you can't remember your password you can reset it by going to iforgot.apple.com and entering your Apple ID (normally your e-mail address) and then reset the password either by sending yourself an e-mail with a link to reset it or by answering some questions on the website.
-Dibbler