When 10 is available and out will it wipe 7 completely when I do the update? I have 10 preview running on a second hard drive right now and I have quite a few programs that will not install. If the update to 10 from 7 keeps all my programs it won't be an issue but I am guessing that is not what is going to happen.
Yes, that is what will happen (mostly). There may be some programs that will no longer work but in the main all your programs and data will continue as they are now.
I've done this from Windows 8.1 several times and everything still worked. Have not tried from Windows 7 and probably won't as the only 7 system I have runs my web server.
It will be an upgrade in place, meaning your programs and data will be retained. Will they work? There are a few threads on TF that list programs that work or have issues. There's also one that is game specific.
List of working apps/programs - Windows 10 Forums
List of Games working on Windows 10 Technical Preview - Windows 10 Forums
Windows 10 bugs - Windows 10 Forums
The above threads include information from many of the TP releases, so read through them - a program or game that did not work in 9926 might be reported as working in a more recent release.
For the most part, Win10 has a good track record and programs run well.
There are a few things that won't install - but they seem to be the install package from the vendor, not Win10.
It's best to image your system on July 28, 2015
See: Backup Complete Computer - Create an Image Backup - Windows 7 Help Forums
Win10 has a Win7 restore feature in Settings. Win8 uses the same mechanism as Win10, so no special recovery tool is needed.
I think there's also a rollback function - the two (restore / rollback) might be the same