A recent experience with M$ installing an update to the Genuine Advantage Tool, which rendered many copies of W7 not genuine has reinforced yet again, that M$ is to be viewed with some caution.
The malicious software remover too, clearly doesn't work. It may in some instances, but given the numbers who still get bothered by malicious software, clearly not enough.
As for something you don't know, that's just a silly risk.
I suggest you turn off updates for XP and do the same in the services. It'll save you a load of resources and keep you clear of M$