Windows 7 is officially unsupported by Microsoft. Use at your own risk.
That said, Microsoft Security Essentials still works, as well as PC Matic, which i haven't used, but has a lot of positive reviews.
Even though Microsoft no longer supports the OneDrive client for Windows 7, you can still connect to your OneDrive quite easily via WebDAV, which is a file sharing protocol that uses HTTPS.
cid in the URL displayed in your browser's address bar.
CID is the code copied in step 2.
Microsoft no longer officially offers any public sources for Windows 7 DVD images, but these links still work as of May 2022:
Unofficial downloads of Enterprise as of May 2022:
Additional ISOs are listed here.
There are some important update packages that may be required to get a new installation to a workable state (including the ability to find and download updates):
This update has two prereq packages, install these three packages in order:
The following list of updates were required for my Dell E6410 after installing the Ultimate x64 image linked above. I've been slipstreaming every update into my Windows 7 install WIM, so my image stays fresh.
Install these in order, skipping any that are already installed: