11-13-2019 07:53 AM - edited 12-18-2019 06:11 AM
Extended Windows 7 support ends January 2020, 10 years after it was introduced.
All 3rd generation Intel Core processors, and later, with a model number starting with 3, for example i5-3470, are Windows 10 capable. Run 'sys info' to see your processor model. If you have a Pentium or Celeron, follow these instructions. If your processor is prior to Windows 10 support, see that section section later in this post.
If you only have 4 GB memory, it is most likely that you will need to upgrade to 8 GB just to run a web browser well (my Win 10 is using 5.4 GB as I type this with only Firefox running), as Win 10 uses more memory than did Win 7, and a 64-bit OS uses more than 32-bit. I recommend Kingston and Crucial "System Specific" memory for your specific ThinkCentre model. If your system runs out of memory, it slows to a crawl.
A free Windows 10 upgrade may still be available, I used this method here a year ago: ZDNet - Here's how you can still get a free Windows 10 upgrade - updated Sept 2019
A few suggestions to avoid problems:
1. If you don't have an automatic back-up program, copy all your user data to a large capacity USB drive(s).
2. If Windows is installed on a hard drive, run a full 'surface scan', as your disk will be using storage it hasn't used before, to ensure it's error free. Run 'Disk Cleanup' as Admin (right-click) on HDD and particularly on SSD to free up storage, select all except for '.. upgrade log files'.
3. If you have a 3rd party security/anti-virus program, such as Norton, McAfee or Avast, since they as so tightly coupled with the OS, it's always best to uninstall before and reinstall after. Make a record of the key before. In some cases, a 'Uninstall program' must be downloaded and run. Check with your security/anti-virus manufacturer.
4. After Win 10 is installed and fully updated, install Lenovo Vantage, and run 'system update'. Also install CCleaner (free version) and run the 'Registry' part of the cleaner. It may take multiple passes to clean fully. Run once every three months afterwards.
5. I like to defer Win 10 feature updates for 4 months, until the bugs are sorted out, and is what Microsoft recommends for corporate users.
I should note that there are many good articles on how to upgrade on the Internet, with more detail than here. This is a baseline of tasks I have done. It may be advisable to read some of those other articles.
If you have an older Intel processor, and wish to use officially supported drivers, updating to Windows 8.1 will give your system another 3 years of Microsoft support. (I am not suggesting that you can't or shouldn't hack Win 10 on an older system, but then you are responsible sourcing the drivers from older Windows versions.)
Update to Win 8.1, 64-bit (which has extended support until Jan 2023), and install the Stardock "Start8" utility to replace the truly awful Windows 8 start menu with a Win 7 like customizable start menu. If your system is new enough, it may already have a Win 8 key, stored in an encrypted format in the BIOS or UEFI firmware, but was downgraded to Win 7. The install ISO file can be downloaded directly from Microsoft, and if needed, a Win 8.1 license (key) can be purchased on Ebay or other resale marketplaces.
Also upgrade your memory if needed, 6GB minimum, 8 GB is better, and follow all the suggestions above, except for Vantage, as your system may not be supported. Instead, go to the Lenovo support page for your system, and update the drivers from there. And there are no feature updates, so no need to defer them. And stop using Windows Internet Explorer (IE) - which comes with Win 8, as it is no longer secure. Use Firefox or Chrome which are much more feature rich, and absolutely necessary from security perspective. Microsoft themselves have said not to use IE except for extreme cases of compatibility where no modern browser will work.
P.S. Apologies in advance to those with AMD processors. I have not had a system with one, know little about them, and their Windows 10 support.