How do I change back from Windows 7 to Windows Vista?

[LDPaul]

Hi, i really need some help here. I am starting to work for sunlife Microsoft Office Enterprise 2007 Serial tomorrow and need my laptop to run Windows 7 X64 Key for their software. Currently i have Office Standard 2010 X86 installed. I want to know if I can split my hard drive and when computer boots I can choose xp or Office Professional Plus 2010 X86. So I can use xp for work and windows 7 for home. Since i don't have the cd for Windows 7 Home Premium X64 I don't want to remove it completely. Any suggestions and help would be appreciated!