M monsieurrigsby Member Joined Nov 27, 2013 Posts 15 Location UK Nov 27, 2013 #1 Hi and hope you can help. This began with the rather generic 80070bc9 Win Update error code when installing updates includes .NET 3.5 SP1 security fixes (2 of these plus a couple of other updates). Following this, I could not install *any* updates (tried them singly). Win 7 Home Premium x64, using MS Security Essentials. Tried from a clean boot but same issue. Since .NET seemed to be implicated, I repaired the .NET installation as per here: Error codes ?0x80070643? or ?0x643? occur when you install the .NET Framework updates There was actually a single ERROR line (couldn't delete some DLL due to use by another process) in the automated cleanup tool log, but it said it was successful. I was able to install .NET 4.5 and 4.5.1 via the MS Download Centre versions but, strangely, the 3.5 SP1 installer would not even run: could see the process running in Task Mgr but then just died. Following all this, Windows Update got stuck in an infinite 'restart to finish installing important updates' loop (with a red cross need to Check for Updates on each reboot). Perhaps unwisely, tried to reset the transactional logfiles as in other similar analyses here; e.g.: https://www.sysnative.com/forums/windows-update/5873-windows-update-in-restart-loop.html However, I couldn't delete files in the TxR folder (in use by other process) in elevated command prompt or even in safe mode with cmd prompt (strange), so I don't think I've damaged anything even if I could have. I attach a ZIP of the CBS folder as requested. Thanks in advance for any advice. P.S. Didn't run SURT before capturing the CBS folder. (The posting instructions don't mention that, though I notice you ask that a lot within individual threads.) The description of what SURT does suggests I may as well try that first, so will do so and repost newer CBS folder when done... May be off to bed soon so that may be tomorrow UK time.