...check your empty drive space available. As you get near end of drive space, windows can take longer to find all the clusters for a particular file, especially if it's fragmented. Have you defragged the computer this year?
I updated my desktop computer from Win7 Pro to Windows 10 about 6 weeks ago, and everything seemed fine (I just upgraded - did not do a clean install). A couple of weeks ago, not sure exactly when, I noticed that saving a new file in Word 2007 takes about 5 seconds. I'm just saving to the internal hard drive, and it doesn't matter what folder it's being saved in. I don't have that problem if I'm logged in as Administrator, only when logged in as a user (I'm the only user).
Is this an indexing issue? I've used the Troubleshooter for indexing, which found no problems, and have deleted and rebuilt the index.
Word 2007 (12.0.6747.5000) SP3 MSO (12.0.6743.5000)
Windows 10 Pro 64-bit version 1511 OS Build 10586.218