First download Win7_ISO_Update.7z and extract it on a drive that has at least 20GB of free space.
Then copy the contents of the DVD install image you wish to update to either the \7SP1-64\ or \7SP1-32\ folder as appropriate.
Finally download the needed update files to the \7RVM\ folder, being:
KB3020369 - Required, Servicing Stack update
KB2670838 - Optional, Platform update, see notes
KB3125574 - Required, Convenience Rollup update
They are all digitally signed (▼ is a direct link to the file, because Microsoft Update Catalog sucks).
For 64-bit installations (497MB total):
▼ | Windows6.1-KB3020369-x64.msu
▼ | Windows6.1-KB2670838-x64.msu
▼ | windows6.1-kb3125574-v4-x64_(SHA-1).msu
For 32-bit installations (325MB total):
▼ | Windows6.1-KB3020369-x86.msu
▼ | Windows6.1-KB2670838-x86.msu
▼ | windows6.1-kb3125574-v4-x86_(SHA-1).msu
Optionally you can also download the Windows 7 Current Cumulative Update (not truly cumulative yet) and save it to the \7CCU\ folder. Look for it amongst the most recent Security Bulletins, it will be described as the "Security Monthly Quality Rollup for Windows 7".
After you have downloaded all the files required, simply run as an administrator the appropriate command (batch) file for the architecture you are using. The finalised DVD image will be created in the same folder as the batch file, note that 64-bit images can only be updated on 64-bit hosts.
If you are updating both 32 and 64 bit images then once that is done you can create a combined image with all versions and architectures by running the merger command (batch) file but the final image will have 2 notable limitations:
- It won't fit on a single layered DVD
- It can't be used for 64-bit recovery
- Be sure to only place one update patch (per architecture) in \7CCU\
- (N/A if using \7CCU\) Windows Update has been taking several hours to just detect (not download & install) required patches for months. German blogger Dalai has created a workaround you can read about here to cut the search time taken back down to minutes.
- The Platform update (KB2670838) is recommended but has been known to cause issues on laptops with hybrid Intel/AMD graphics, see the knowledge base article for details.