Download the beta again.
I also used to have installation problems, but, when I checked the MD5 hash of my copy of the iso and I saw that it differs from another iso that worked.
Here is a list about some information for the two ISOs Microsoft offers...
x86
- File Size = 3.12 GB (3,355,598,848 bytes)
- CRC Value = 0x67E089E0
- MD5 Value = 0E733AB1A8E8FF9A8684FD3639332773
x64
- File Size = 4.01 GB (4,309,368,832 bytes)
- CRC Value = 0x48697711
- MD5 Value = E43502D0A15EADD551119D5639859E04
Download
Damn Hash Calulator and check the MD5 or CRC hash against the ones I posted above depending on your ISO edition.
If they are diffrent, then I'm afraid that your copy is corrupted, and you'll need to download it again...
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