+1  A: 

Should not conflict.

Daok
+1  A: 

I did D2007 on the same machine as D2006 with absolutely no problems (I was shocked, actually).

I haven't tried D2009 yet, but it should be ok.

This guy had problems though. Hopefully his issues were due to the custom setup he describes in that article.

JosephStyons
+1  A: 

A colleague of mine (think he has an account on here as dcraggs now) has got them both running on the same machine just fine, I believe.

Certainly would be a huge own-goal from Embarcadero if installing D2009 broke an already-installed D2007, given the way that the components and DCUs are not compatible - I suspect a fair number of people will need to have both around for a while (some of us still need D5 and D7 too!)

robsoft
A: 

CodeGear stated (don't have a link handy, sorry) that there should be no conflict. I haven't yet installed D2009 on my workhorse PC so I don't know if that is correct.

The settings in registry have different path and packages have different names so there really should be no problems.

gabr
A: 

I have Delphi 2007 and I have installed 2009 yesterday with no visible problems so far. Both seem to work fine.

TOndrej
+2  A: 

I have at least 4 Delphi versions on one machine. They do not bite each other.

I always install older versions first because i had once problems if i did this the other way round.

Gamecat
A: 

Appears to be no problem. Installed D2009 with TurboDelphi and 2007 and 2, 5 and 7 all on the same Vista machine

Both 2007 and 2009 have Jedi JVC and JVCL installed on them. All appear to work fine. Hope that helps.

+4  A: 

I am running 2007 and 2009 on the same machine (this machine) just fine. The only problem you might have is if you are compiling components to the same directory - you will just need to rebuild all your DCU's and packages each time, or make version specific packages and directories.

Jim McKeeth
A: 

.. and if you compile existing packages make sure you give them a new name (e.g. suffix with D12) as each version's BPL directories are in the path.

+4  A: 

Install them in their own directories, and make sure you keep package binaries separate, you should be fine. I've got 2009, 2007, 2006, 7 and 5 all on this machine with no issues.

Malcolm Groves
+17  A: 

All new versions of Delphi can always be installed safely /next/ to older version.

Each new version should be installed in its own directory.

If you are going to install multiple versions, always install the oldest version first, and then work your way to the newest.

We work very hard to make sure that all versions of Delphi coexist together. But again, never install one version directly on top of another.

Nick Hodges
+2  A: 

Yes - as Rob said (Robsoft) I have both working here. Delphi has always been very good at co-existing with other versions.

Obviously you can only have one version as the default for opening Delphi files.

dcraggs
A: 

Installed D2009 Enterprise on VMWare instance running Vista Business with an existing D2007 Enterprise installation. Perhaps I did something incorrectly, but I began to experience errors in the D2007 IDE, as well as a very strange error, unknown fieldtype, in exe files compiled with D2007. I uninstalled D2009, and the errors have gone away.

Bill Seven
A: 

You should always install the older version first. I tried to install 2009 first and then 2007 but the setup of 2007 failed.

Uninstalling 2009, and starting with 2007 first fixed the install problems.

smartins
A: 

In theory, it's possible, but if you use many third-party (or your own) libraries, it can get hairy pretty fast. I tend toward developing on Virtual machines, for this and other reasons. But, YMMV.

Jamo
yes that's what I am doing, but not ideal really. Fed up of moving from one to the other.
Steve
I just use shared folders, and run both VM's at the same time when needed (which, if you have enough CPU and memory, is doable).
Jamo
A: 

Should be fine. I have Delphi 7, 2006, 2007, 2009 with 3rd party libs Dev Express and Rem Objects for all (except Dev Express for 2009 - is it out yet?) and all work flawlessly. As others pointed out the versions were installed oldest to newest.

gcrombie
A: 

The installations won't interfere with each other, although the Delphi 2009 and Delphi 2007 projects are not compatible, and can't be shared.

Mmarquee
A: 

Moving along with the order of release is a must. Install older first. Uninstalling may get tricky though. How to fix Delphi 2009 data explorer?

A: 

what about system path? is it set for delphi2009 or 2007? Path=C:\Program Files\CodeGear\RAD Studio\5.0\bin; Path=C:\Program Files\CodeGear\RAD Studio\6.0\bin;

which one should i set?

enginm
Rad Studio 5.0 is D2007 and Rad Studio 6.0 is D2009. Just leave both in the path. The only problem you may have is if you run the command line compiler DCC, in which case, you should specify which path you want in your script.
Steve