INSTALLATION

1. Extract the contents of the archive on your computer and navigate inside the extracted pt_countdown folder
2. Using your FTP or SSH client upload the following directories to your store root directory. This will not overwrite any file.
    app
    skin
3) Edit "catalog.xml"
    It's located here: /app/design/frontend/default/[YOUR-THEME]/layout/catalog.xml.
       (for Magento versions 1.4.X.X, if you use default theme, look for this route: /app/design/frontend/base/default/layout/catalog.xml)
        For example, if your design folder name is "default":
            /app/design/frontend/default/default/layout/catalog.xml
        Or if you are using "modern" theme:
            /app/design/frontend/default/modern/layout/catalog.xml
    Edit the file and go to "<catalog_product_view>" section and search for this string (under this section!).:
        <reference name="content">
    Add below this line:
        <block type="catalog/product_view" name="product.countdown" as="countdown" template="paytype/countdown/countdown.phtml"/>
4.Refresh your cache from Admin Panel: System > Cache Management
        Set "All Cache" to "Refresh" and "Save cache settings".
       (for Magento versions 1.4.X.X simply click on 'Flush Magento Cache' and 'Flush Cache Storage' buttons)
5. It's done!

ADMIN PANEL OPTIONS

You can modify some options from Admin Panel. Settings are available from the System -> Configuration page, under Catalog tab. You will find there "Sale/Promotion Countdown", click it.
    Enable this extension
    Enable for products with Special Price
    Enable for catalog promotions
    Countdown box Background color = use HTML color codes (i.e. #dd7676)
    Enable gradient on background = enable or disable gradient color effect
    Description text = i.e. "This sale ends in"
    Countdown display format = %%D%% will be replaced by remaining days, %%H%% by Hours, %%M%% by minutes, %%S%% by seconds.
    Finish message = this message will be shown when timer finishes.
    Text - Font size (px) - Font size in pixels, enter only integer number.
    Font Family - Name of font. i.e. Arial
    Margins (px) - if you are using a custom theme, this property can be interesting. For modern theme I would set bottom margin to 20 and right margin to 15...

TIPS

Q) I want to disable the sale countdown for all products, except one.
A) Try this way:
     - Go to System -> Configuration page, under Catalog tab. You will find there "Sale/Promotion Countdown", click it.
     - Disable the countdown using "Enable this extension" field.
     - Now go to Catalog > Attributes > Manage Attributes and create a new one called enablesalecount
     - Associate it to the attribute set of the desired product on Manage Attribute Sets
     - Edit the product, and set the enablesalecount attribute to 1 (will force the countdown display).