xp machine not vsible form W7 machine

beware99 said:

He guys thank you for your help, but you all seem to miss something I wrote.
I see the XP machine right now because I did a system repair yesterday on the W7 machine.
The thing is that it might work well today and that I can not see the XP machine tomorrow.
If that happens I fix it on the W7 by doing another system repair (back to the situation from yesterday).
So, the problem is in the W7 machine and not in the XP, right?

I tried to install the LLTD but get an initializing error (0xc0000135) .

That is incorrect. The hotfix needs to be installed on XP with sp3.