WIN7有一个保留的引导区，惠普和现在很多装Win7的机子都一样的，可以装Win XP的呀，不过启动项有一个地方是要变更的。具体我就不清楚了，我们公司的IT给我装的时候，改变引导区就能装上XP了。然后多出出来一个隐藏的硬盘分区。你可以在网上找一下如何在格式化Win7后装XP。

Solved!
1. Install WIN7 in Oracle Virtualbox, but remember that the VT-x/AMD-V option must be enabled;
2. For XP installation in Virtualbox , copy directly the existing .vbox file from another PC to the willing physical place of Pavilion g4.
Now, by Oracel Virtualbox, we can install SAS9.3 or SAS9.1.3 in HP pavillion g4 notebook.