Complete Loss Of Desktop Functionality After Upgrade

I have a custom built computer with the following relevant internals:

Intel Core i5-3750k Ivy Bridge Quad-Core 3.4GHz (3.8GHz Turbo)
ASUS P8Z77-V LE LGA 1155 Intel Z77 HDMI SATA 6Gb/s USB 3.0 ATX Intel Motherboard
G.Skill Ripjaws Series 16Gb (4.4GB) 240-Pin DDR3 SDRAM DDR3 1333
ASUS HD7850-DC2-2GD5-V2 Radeon HD 7850 2GB 256-Bit video card
Samsung 840 Pro Series MZ-7PD128BW 2.5" 128GB SATA III Internal Solid State Drive

I was using Windows 7 with an external wifi adapter for internet access and the computer was perfectly fine. Upon upgrading to Windows 10, I instantly ran into issues that quickly grew worse. From the get go, I was unable to utilize anything on the taskbar, including icons that I placed there like Chrome and the newly installed Edge. The search bar was likewise inaccessible and now, after multiple restarts, I can no longer use the Start button with either mouse or keyboard. The internet icon on the taskbar will not work and even when attempting to access the internet after hitting ctr+alt+del, I find that the computer cannot even detect a connection, even though I know it should be able to. After a few minutes trying to mess around with other fuctions, the entire computer basically freezes and the entire computer locks up forcing a hard reboot.

Pictures and videos will not load (I can click on the My Computer icon on the desktop and access everything there), the computer telling me the files are corrupted. Same goes for documents, and games will not launch (Steam obviously cannot connect).

For lack of a better term, this issue is... weird. It's like I only have selective functionality over certain programs, although its selective enough that it has basically rendered my PC useless. I cannot even figure out how to uninstall Windows 10 because I can't access the Start menu.