The thing you would need to change there is seen when booted into 7 not XP since the 7 BCD store is what manages the boot loader.
Since you are unfamiliar with the EasyBCD tool and not running Vista you will wonder why the 7 boot splash screen will be replaced by the Vista boot screen instead when using the 1.7.2 currently available.
Another free tool called BellaVista can easily change the default OS without making other changes or need any installation. System Tools - BellaVista
The quick and easy method however is to simply go into the boot tab found in the msconfig utility and set XP as the default there or in the Startup and Recovery settings mn9500 pointed to there.