Can you make it say anything above 7.9 by hacking?
Yea, you can go as high as 9.9

But that would be spotted to be a fake immediately because it's not supposed to go any higher than 7.9...
Info on how to do this & no reboot is required so you can check the
WEI as you do it to make sure you are editing the correct numbers.
The Windows System Assessment Tool (WinSAT), is a free benchmarking tool that measures various performance characteristics and capabilities of a computer running in Windows Vista, Windows Server 2008 & Windows 7.
The ratings are displayed as Windows Experience Index or WEI score.
The hack stuff:
WinSAT saves the scores in a XML file located in the
Windows\Performance\WinSAT\DataStore folder.
Each time you perform benchmarking using WinSAT, it creates a new XML file and stores it in this folder.
All you have to do is to open the latest XML file and edit it using WORDPAD.
hackscore
Fun stuff: Modify your WEI score and show it to your friends just for fun.
What this looks like in Wordpad & the numbers to be changed.
(This is just the first part of it as the data is quite extensive & is toward the top or start of it)
System Assessment Tool</Title><ModulePath>C:\Windows\system32\winsat.exe</ModulePath><CmdLine><![CDATA["C:\Windows\system32\winsat.exe" formal -cancelevent cf218779-9458-4221-bd5f-311f3dfce91f]]></CmdLine><Note><![CDATA[]]></Note></ProgramInfo><SystemEnvironment><ExecDateTOD Friendly="Thursday June 25, 2009 2:42:05am">733583:9725092</ExecDateTOD><IsOfficial>1</IsOfficial><IsFormal/><RanOverTs>0</RanOverTs><RanOnBatteries>0</RanOnBatteries></SystemEnvironment><WinSPR><SystemScore>
7.9</SystemScore><MemoryScore>
7.9</MemoryScore><CpuScore>
7.9</CpuScore><CPUSubAggScore>6.4</CPUSubAggScore><VideoEncodeScore>
7.9</VideoEncodeScore><GraphicsScore>
7.9</GraphicsScore><Dx9SubScore>6</Dx9SubScore><Dx10SubScore>6.8</Dx10SubScore><GamingScore>
7.9</GamingScore><StdDefPlaybackScore>TRUE</StdDefPlaybackScore><HighDefPlaybackScore>TRUE</HighDefPlaybackScore><DiskScore>
7.9