My PC has been blocked and i believe it could be a scam.

i was on my laptop when my screen a federal government symbol and a message that i had visited a site which caused my computer to be blocked and i would need to to purchase a $300 pay money pak and pay a fine for visiting.And the fine must be paid within 72hrs.

Have you sought assistance from your resident antimalware program (AVG, Avast, Avira, McAfee, Norton, etc)?

You've been infected with one of the latest versions of ransomware.

Try going into Safe Mode, download/install/run Malwarebytes Free:

Go to www.malwarebytes.org and download, install, update and run the free version – just follow the prompts.  Select Download Free – at the end of the installation is a dialog with 3 check boxes:  The first option is to Enable Free Trial of Malwarebytes Pro and you must uncheck the first option to install the free version without real time protection enabled.   You may need to rename the installation file to 123.exe or something similar to prevent the malware from disabling/blocking the installation.  Or you might want to download the installation file to a flash drive or CD and then install Malwarebytes on the infected computer.

And/Or

One of the Answers Forum users maintains an excellent guide on computer security matters to include removal of this “ransomware.”  See the following compliments of  Brian M- for suggestions on how to resolve your problem:   http://www.selectrealsecurity.com/remove-ransomware/

And/Or

The malware you are describing is a variant of the so called FBI Moneypak malware...the instructions in this "blog" will probably help you remove it: http://malwaretips.com/blogs/remove-fbi-alert-moneypak-virus/

Hope this helps...

How to remove FBI MoneyPak

http://malwaretips.com/blogs/remove-fbi-alert-moneypak-virus

 If that does not work:

**If you are using Microsoft Security Essentials,**start here - https://support.microsoftsecurityessentials.com/ and select the link that says - I think my computer is infected. Options will vary by region, but phone support leads you to Microsoft Answer Desk (http://www.answerdesk.com/)in the US at this time. After an initial free consultation, a fee will be charged for assistance, based on the details of the case.

**If not,**go to **** your AV provider.

You might also try this web site - http://www.bleepingcomputer.com - contains details for many of the common infections, often immediately after they began to appear in the wild, and instructions are provided for how to remove the infections using their malware removal guides. They also have forums where you can seek help from people who specialize in malware removal.

These are other free programs that may help:

Malwarebytes Free - http://www.malwarebytes.org/products/malwarebytes_free  Please note: The final install dialog at  provides a pre-checked option to install the Pro trial. To install the free version, you need to uncheck that option.

Superantispyware Free - http://www.superantispyware.com/downloadfile.html?productid=superantispywarefree

TDSSKiller (free) - http://support.kaspersky.com/faq/?qid=208283363

HitmanPro (free for 30 days) - http://www.surfright.nl/en/hitmanpro