Welcome to windows7forums, Hector.
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To enable Aero:
copy this to notepad and save it as
Aero.reg, then double-click on Aero.reg and confirm changes:
Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\Software\Microsoft\Windows\DWM]
"Composition"=dword:00000001
"CompositionPolicy"=dword:00000002
Reboot.