The recommendations over at the Steam forums are to allow Steam to finish updating while running Windows in Safe Mode - presumably some background application (like a third party firewall or antivirus program) is preventing Steam from updating in these instances.
To restart your computer in Safe Mode with Networking support you can do the following;
- Load up Steam, wait till it's stuck on 99%.
- Press "Start" button, type "msconfig" into the search bar and press enter.
- Under the "Boot" tab where the "Boot options" are, tick "Safe boot" then select "Network".
- Restart your computer and allow it to load up in safe mode.
- Everything will most likely look big and ugly.
- Load up Steam, once it completes the update, log in.
- Press "Start" button, type "msconfig" into the search bar and press enter.
- Under the "Boot" tab where the "Boot options" are, un-tick "Safe boot".
- Restart in to normal Windows.
- Run Steam successfully.
As an alternative to running msconfig to force Safe Mode with Networking, it is possible to achieve the same effect by pressing F8 at the correct point during Windows startup (just before the Windows logo first appears, after the power on self test has completed).
This of course, might not be the only solution to the problem you're experiencing. One other suggestion for resolving this problem is that by closing Steam and then deleting the clientregistry.blob file from within your Steam installation folder, you can complete updating the Steam client successfully.
Finally one other solution that I haven't come across before is using a utility called TCPView to close the connection from Steam during the update process, after it has stalled. This is detailed here in this Steam forum post and involves using a free Microsoft Sysinternals application called TCPView. The details on how to achieve this are as follows;
- Download the TCPViewer application from Microsoft MSDN
- Extract and run the TCPView.exe application only
- Open the Steam, when it hangs during updating, open the TCPView.exe and find steam.exe inside the TCPView.exe program
- Right click Steam.exe inside the TCPView programme and click close connection.
It could also just be that in the year or so since you've last used Steam on this computer it needs to download a sizeable update, which could take some time. The Steam updater can leave itself in a position where it looks like it's doing nothing but may require just a little patience before it springs back into life.
