Dell Inspirion 560s Desktop
Unable to upload another new OS

This is with referance to Purchase of "Dell Inspirion 560s Desktop" through "Invoice No.00399148 Dated:26/01/10

I wanted to install new OS of Xp service pac 2 because there are some application which are not supporting to window 7 home basic, as i install another OS at the time booting it not showing two option XP get directly started so for window i have again install the window 7 so pls help me in installing the another OS or arrange an Engineer for the same.