Problem installing Half-Life 2

[MrVamp666]

When I'm installing Half-Life 2, this pops up: "Error 1305. Error reading form file; C:\Program\Files\Valve\Steam\SteamApps\half-life 2 content.gcf. Verify that the file exists and that you can access it."
:dozey:
And whatever I do it never gets past this thing. Could someone please help me?