Dungeon Defenders PC System Requirements

For anybody who is wondering if their computer can run the game, here are the system requirements and recommendations for PC.

Minimum:
• OS: Windows XP
• Processor: 1 Ghz Dual-Core CPU
• Memory: 1 GB RAM
• Hard Disk Space: 2GB
• Video Card: Graphics Card with Shader Model 3 support, 256 MB video memory
• DirectX®: 9.0c
• Sound: DirectSound-compatible sound device
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Recommended:
• OS: Windows 7
• Processor: 2Ghz Dual-Core CPU
• Memory: 2GB RAM
• Hard Disk Space: 2GB
• Video Card: Graphics Card with Shader Model 3 support, 512 MB video memory
• DirectX®: 9.0c
• Sound: DirectSound-compatible sound device
Source
If this doesn't solve your problem, you can use this website to determine if your computer can run it, by selecting Dungeon Defenders from the dropdown menu, or searching for it.
You can also download the demo from here if your still not sure.