Your device uses a screen resolution of 320 x 480 pixels, while the application you're trying to run needs a minimum of 800 x 480 pixeis.
While you are using an application to manipulate the Screen Density, this can't overcome the physical limitation of your device's screen, that the application checks for before running.
In short, you can't run the application on that device.
Elaborating the Answer
Your device, the Samsung I5700 Galaxy Spica uses 320 x 480 pixels of screen resolution.
PokerStars Mobile Game
The application you've mentioned in the question comments, under the FAQ section says:
Does PokerStars Mobile Poker work on all Android devices?
No. PokerStars Mobile Poker is designed only for mobile devices running Android™ 2.2 and above, with a minimum screen resolution of 800x480. Compatible devices include (but are not limited to):
- Samsung Galaxy
- Galaxy Nexus
- Motorola Droid RAZR
- HTC Sensation
- HTC Desire
- Sony Ericsson Xperia X10
- Sony Ericsson Xperia X13
- Acer Liquid A1
What is Screen Resolution?
Quoted from Android Developers - Terms and Concepts
The total number of physical pixels on a screen. When adding support for multiple screens, applications do not work directly with resolution; applications should be concerned only with screen size and density, as specified by the generalized size and density groups.
Actual physical size, measured as the screen's diagonal.
For simplicity, Android groups all actual screen sizes into four generalized sizes: small, normal, large, and extra large.
The quantity of pixels within a physical area of the screen; usually referred to as dpi (dots per inch). For example, a "low" density screen has fewer pixels within a given physical area, compared to a "normal" or "high" density screen.
For simplicity, Android groups all actual screen densities into four generalized densities: low, medium, high, and extra high.