Friend's xp pro pc (legal copy)

Windows update reports sp1 critical update is required.
Half way thru d'ld/install error is displayed - "server
cannot be reached". After multiple retrys a link to sp1a
express is offered for manual install.

Question is:
1. Being as the pc has some sp1 hotfixes currently
installed and running msjava, what will sp1a do to these
hotfixes and the java?

thx
Teris