Vista SP 1 -download unsuccessful

I have meanwhile tried for 8 times to download the Vista SP1. All seems to work fine until I get to the last part (3 of 3) when the system detects some error (not furtherdescribed) and completely de-installs the download.
I have faced this problem since March 2008. No matter which way I try to install the update - it is never a success. I have activated the automatic download and all other patches, updates etc. have been successfuly installed. At least accoding to the system. I question if I need the SP1 at all. Hope someone out there can shed some light on this issue.

What I have noticed is that in the tool manager the WAN Miniport (SSTP) shows a yellow caution mark. I can work with all installd applications without problem, even that I have installed a small private network.
Regards, helplessmike