reburned the DVD, it's working now.
but I get a error message at the end of the installation, using guid now.
ps I'm typing from my iPod touch

Edit:
now I'm having the blinking cursor at boot, I'll try to install EFI manually

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Mac Inspiron 531 » 10.6.8 • 10.8.0 Legacy Kernel • AMD Athlon 64 X2 5000+ (2.60GHz)
Dell M2N61-AX/nForce 430/MCP61 • 4GB Dual Channel DDR2 667MHz
ALC888 • nVidia GeForce 8600 GT 256 MB
2 x WDC WD5000AAKS 500 GB SATA HDD