Why can't I buy HD movies on iTunes for Windows?

Hi,

Was hoping someone could help me with an issue I'm having trying to purchase HD movies on iTunes using a Windows 7 system.

When trying to purchase the movie in HD, I get the following message:

The thing is, I was able to buy 3 HD movies previously, but over the last few months, it hasn't been working. When I close the above window, it takes me to the system requirements, which I think I have.

Windows System Requirements for HD content:

• 32 or 64-bit version of Windows 7; Windows XP and Vista do not support HDCP
• iTunes 10 or later
• 2.0 GHz Intel Core 2 Duo or faster processor
• At least 1 GB of RAM
• A video driver that supports HDCP (you may need to check with the manufacturer to determine if your video driver supports HDCP)
• A display that supports HDCP with a screen resolution of 1024x768 or higher with a digital connection (DVI, DisplayPort, or HDMI)

Here are my system details:

Windows 7 Home Premium

Dell Inspiron 537S

Pentinum (R) Dual-Core CPU ES300 @ 2.60GHz 2.60 GHz

4.00 GB RAM memory

64-bit Operating System

iTunes 10.4

The only ones I'm not sure about are the last 2 bullets. I called Dell and I was told I didn't need a new monitor, but just a video card. I didn't trust the representative's answer too mcuh.

Does anyone know what I'm missing to be able to purchase HD movies?

If it helps, the movie I was trying to purchase was Transformers: Dark of the Moon

Thank you!