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

[SaulVT]

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