>I am thinking of upgrading to VFP6 from VFP5. Can anyone tell me if VFP5 still run normally if VFP6 is installed alongside, or does VFP6 overwrite some dll's etc that VFP5 will then try to call?
>

They can coexist quite easily; I run both. The runtime and development engines are independent. A few gotchas to watch:

(1) The handlers for various programs associated through the registry will be altered by the installs. The rule seems to be last man standing - whichever version of FP installed last on the system will be assigned as the default handler for FP-related file extensions when you double-click from the browser.

(2) The ActiveX components distributed with each and their handlers are different. You may run into problems with different versions of some ActiveX controls when both versions are present; you need to be careful that the version ypu use in your forms is registered, and when creating distribution sets, is distributed with the Setup.

(3) The Tools/Options settings for each in the registry use different registry keys, so Tools/Options setting need to be done for each separately. If you want to duplicate the way you set them up, you'll need to copy the registry settings to the appropriate subkeys or set them by hand. I'd also do something like setting a different dfault icon and/or caption to make it easy to see what's running on the taskbar.

(4) Be careful about things like FOXUSER resource files and CONFIG.FPW which are affected by search paths, and might come in at unexpected locations.