Hi there JimmyDA Welcome to Subsim
1. Windows 7 Support ends on 14/1/2020
to save yourself some money and heartache go with Windows 10
Link to end of Windows 7 Support
https://www.microsoft.com/en-gb/wind...rt-information
2. I would just transfer your SH3 Game Folder to a USB stick then transfer it to New Computer not forgetting the SH3 Folder in your Documents with your Career Saves ect
Or just a clean install of SH3 then run the stock game first then install all your Mods then run SH3 see if all goes well if so then copy n paste your SH3 Folder with your career histroy to your new pc's documents folder and you should be ready to rumble where you left your old campaign install.
3. 2020 is going tobe a big Year for computer Tec would be good if you could wait untill Spring May - June Time Ryzen III and Intel CPU'S will probably drop in price due to Ryzen 4000 Launch
4. if you run into any Problems or issues with your New Pc installing running SH3 and Mods Subsim Members will help you get squared away
At Subsim the pride runs Deep we look after our Own Salute