Default HTC First Help!

Hello, I accidentally deleted my system UI on my HTC First while trying to flash a custom ROM. As of right now I can load into TWRP and H-Boot, but I can't seem to get ADB Sideload working. Every time I do load it my computer shows it in portable devices with the name E:\ and in Android USB Devices as MY HTC in the Device Manager but I cant access them anywhere on my computer. I have the stock files for the First along with the boot.img. If anyone can help I would really appreciate it. Thanks.