Screwed Up System Configuration

I did a bad thing, while trying to resolve an issue with RealTeck PCIe GBE family controller on one of my two ASUS desktops. I have 3 desktops connected to my router and home network via CAT5 cables. The initial problem is no internet access tied to IP address being invalid. What is interesting is the two ASUS M11AD desktops are exhibiting the exact same issue but my other desktop and laptops are functioning properly. It seems strange that both RealTek hardware would fail at the same time. Thus, I suspected the driver and was able to update the driver; but that didn't resolve the problem. I do not have a wireless device to troubleshoot the hardwired RealTek and plan to purchase one today.

With regard to the system configuration, I was following an online suggestion to try something in SAFE mode and changed a few settings. Unfortunately, I didn't write down exactly what I was doing and now cannot get my granddauther's desktop back to functioning properly. Now, whenever I enter "System Configuration," the dialog box that pops up does NOT indicate "normal startup" but shows "selective startup". Also, when I look at control panel, the only network device is the RealTek adapter and none of the other items which previously had appeared in the list.

Thank you in advance for any assistance that anyone can offer to resolve this system configuration issue. I would also appreciate assistance/suggestions regarding what maybe askew with my desktops not having LAN connectivity.

 

Is my screw-up and dilemma beyond fixing?

 

What operating system are you on? Are there link lights on the router and network cards?

 

Sorry for not responding sooner and thank you for attempting to assist me in this mess. The OS is Win10. As for router and NIC lights, I can't be certain as I didn't check them. The computer was connected to the router via a Cat5 home network. I just kept getting message regarding unable to connect. I have since purchased a TP-Link AC600 USB wireless adapter and have it installed but am unable to get connected to the network.

Since posting the initial message, I have experienced several occasions of failure to access the internet on other computers and cell phones. At this point, I am seriously considering replacing my ASUS RT-N56U wireless router.