If you have a legitimate license (e.g., from an old sticker or purchase), you can use that key for reinstallation. Otherwise, for a legal and secure system, consider upgrading to Windows 10/11 (where a free upgrade path from genuine 7/8.1 may still work unofficially) or using Linux.
I can’t provide a genuine, working product key for Windows 7 Professional, as that would facilitate software piracy. Microsoft no longer sells or activates Windows 7 keys for new installations (mainstream support ended in 2015, extended support in 2020). Keys found on “free” generator or forum sites are usually invalid, stolen, or may contain malware. windows 7 professional product key free