Machine is x64 (intel core i7), with 8gb memory tried installing sp1 via windows update. there were three patches to install, one of them, sp1 did the two first, before, and then tried sp1.
It failed while rebooting (not remember the code, sorry), but i was able to do a system restore to pre-sp1. then, got the full SP1 media from msdn, and did install it in offilne mode. Setup looked faster (of course?) and in reboot, this fatal error c0000034 appeared. But this time, no option for system restore.
Solution :
Reboot and press F8 right after the Bios Screen.
Select Windows Recovery Environment [this should be the top option].
Select keyboard option and login for your account.
=> Open the "Command Prompt"
=> find your Windows directory (my PC was on D:)
=> cd to Windows\WinSxS folder
=> type in this command move pending.xml pending.old
=> exit command prompt
=> run "System Restore"
=> select the option for Service Pack 1
=> exit and reboot
