<SOLVED> I broke my video, ATI card runs in Software Rende

[jeparham]

UPDATE

I found instructions that showed how to do a "repair install" of Mint. Following those instructions, I successfully repaired my video issues.

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In an attempt to get a game to work better graphically, I made what now seems to be a foolish attempt to install the latest drivers I downloaded off AMDs website. I never was able to get the driver to install, and since it was late I just gave up for the day. Last night I booted into Mint, and I had a multicolored scrambled display. I tried multiple things I found on various help forums, and while I have been able to get back to my Mint desktop, I get the pop-up alert that Cinnamon is using software rendering mode.

I checked the Driver Manager, and there are four choices listed, but they are ALL greyed out and none of them can be selected. The one that is currently selected is the last one that reads "Continue using a manually installed driver." At the bottom of the window it reads "No proprietary drivers are in use." So at this point I don't know what I've done or, more importantly, how to fix it.

This is the output of inxi -Gx:

xxxxxxxx ~ $ inxi -Gx
Graphics: Card: Advanced Micro Devices [AMD/ATI] Juniper XT [Radeon HD 6770] bus-ID: 01:00.0
X.Org: 1.15.1 drivers: (unloaded: fbdev,vesa) Resolution: 1920x1080@60.0hz
GLX Renderer: Gallium 0.4 on llvmpipe (LLVM 3.4, 256 bits) GLX Version: 2.1 Mesa 10.1.3 Direct Rendering: Yes

This is on Mint 17, 64 bit.

I have not been using Linux all that long, and I don't have a clue what I need to do. Can someone please tell me what I need to do to repair what I've done?

Thanks

[AUserInEssex]

I can't really help, but I can say I've got a similar problem - similar problems, in fact. (1) I messed around with drivers and subsequently sometimes I get a weird flickering, whereby some of the desktop shows through windows. (2) On the beta of Cinnamon 2.4, I am suddenly stuck in software rendering. (I know one should expect problems with beta software. Also, I have backups, but they are from quite a while ago . .)

[AUserInEssex]

This fixed the problem for me (although there were some graphical oddities, briefly, just after the reboot):

sudo update-rc.d -f mdm remove
sudo update-rc.d mdm defaults

Then reboot. (I found this solution on an Ubuntu forum.) It may or may not work for me (and I admit that I don't really understand the solution I've just posted - though, as I say, it worked for me).