I'm planning to replace my aging Geforce 8800 GTS 320MB with a newer card in hopes of being able to play newer games at higher resolutions than 1440x900 and with better settings. I've decided that I will buy a Radeon HD5770. My mobo only supports PCIe 1.0 but I've read that mid-range cards don't really need all the bandwidth that PCI2 2.0 provides and that the HD5770 shouldn't suffer from loss of performance.
I have some questions before buying the card so any help and insight will be appreciated:

- ¿Do ATI cards perform well with most modern and old games or is the compatibility below nVidia cards?
- ¿Am I wrong assuming that the HD5770 will work well in a PCIe 1.0 slot? ¿Has anybody done this before?
- ¿Will SecuROM protected games prompt me for reactivation if I change only the graphics card? ¿Should I deactivate every game previously?
- ¿Will GFWL games ask for reactivation too? If that's the case maybe I'll postpone the change until I finish some of those games.

1. They perform around the same.

2. Yes PCI-e 2.0 cards will work fine in a PCI-e 1.0 slot, albeit at PCI-e 1.0 speed.

3. No, the game should all be fine.

4. Again you should be fine. Only mobo/cpu replacement and a few other things would mess up your games.

it shouldn't matter it should work fine. It depends on the level of implementation. If you have any games installed that required activation, it would be a good idea to see if the games have license revoke tools and run them before changing the card. This can sometimes be done without having to uninstall the game so it would only require another activation after the new card was installed. A game can use GFWL and have other 3rd party protection as well so it would depend on the game. For the GFWL part, it usually just requires entering the key.
It basically boils down to:
- where it was purchased (i.e. online distribution and what forms of DRM (if any) were added by them.)
- what DRM the publisher used

I have changed cards and not been prompted to reactivate.

I'm marking this as the solution because of that part but everybody gets rep, thanks. My mobo is Intel so I guess I should be fine.
One more question that I forgot to ask: ¿Should I uninstall the nVidia drivers before installing the ATI card?

@HampsterStyle: I was referring to the GFWL activation only not he 3rd party DRM in my last question. GFWL has limited activations for Live so if I use all of them I won't be able to play MP or earn achievements anymore.

Use a driver cleaner first then install new card then install new driver.