If your internet connection is not stable after a hardware upgrade, try the following steps:

1. Reboot your computer and modem
2. Turn off any power-saving options enabled on your computer and/or modem
3. Verify that your DNS settings are configured correctly
4. Check to see if there are any updates or new versions of your network card drivers or software
5. Disable any firewalls or anti-virus software that may be blocking your connection
6. Change your wireless security settings
7. Verify that you are using the correct internet connection type (wired or wireless)
8. Ensure that your modem is connected securely to your internet service provider (ISP)
9. If all else fails, contact your ISP to troubleshoot the issue