|How do you define dangerous?|
Linux and xp can live in different partitions on the same disk no problem. 512meg of ram is not enough for xp if you expect normal performance.
I prefer three partitions, one for each os and the 1st primary as the partition that has all of the boot files [system files in microsoft speak]
Though these days its common to virtualize the OS as a guest [means you run xp, then run the guest OS linux in a virtual machine] we have to come back to the fact you don't have enough memory to do virtualization.