Hello. First of all let me say this is virtually the same process for all x64 Windows versions 7, 8, 8.1 and 10. I haven't tried this on Win XP x64 but i'm sure it should work as long as your plugins officially support or at least work under Win XP x64.
The need for native x64bit operation has risen from the always expanding need for the various Vst instruments to access more ram. It's not a secret that all the good sample libraries in the various software samplers like Ni's Kontakt or VSL are so demanding in ram, that they go well beyond the physical limitations of a 32bit Windows OS. Especially when you need to run 8 or more orchestral parts in ie. Kontakt. So how to work with those x64 plugins natively since Acid Pro is a 32bit application?
JBridge, which costs about 20euros, is known for bridging 32bit plugs to 64bit so users can utilize their favorite 32bit vst plugins in 64bit host software that doesn't support 32bit plugs, without paying to upgrade their various vst's. What is not well known about this little bridge software, is that it can do the opposite as well, which means running 64bit plugs inside a 32bit DAW like Acid Pro. The advantage is that the bridged plugs still conform with the x64 paradigm, meaning they "take" ram from the OS instead of the host software, in this case Acid Pro.
The procedure is simple.
1) install your x64 vst fx and instruments in a folder, most of us usually name it "VST plugins"
2) make a new folder and name it something you can distinguish from the original vst folder. I name it "Bridged plugs"
3) Run the Bridger which is the executable part of Jbridge. What you have to do here mainly, is tell the app you want to use a 32bit host, choose to save the Bridged versions of your plugs in the new folder you already made and let the app read/scan your 64bit vst plugin folder. After a few seconds (depending on how many plugs you have there and how fast is your machine too) new 32bit versions of your x64plugs will appear inside the folder you selected ,in my case the "Bridged plugs" folder.
4) Run Acid Pro and set/add the "Bridged plugs" folder in Acid's vst plugin preferences. Acid will work with 99% of the bridged software. I run a bridged Kontakt 5.5 with 8Dio's Orchestral libraries utilizing 14gb on a 16gb/i7 machine with no sweat.
What about the Vst fx plugs though ? Most pro users have an abundance of these, i know i do. What i will describe next, came from the need to map and control multiple vst fx at the same time from one hardware controller without hours of programming and assigning midi controller data and saving templates. Welcome to NYRV Agent (99 euros atm). This charming vst plugin is actually a plugin host for vst fx that lets you easily assign parameters with midi learn in every plug you open inside it, all in a unified, easy to use and easily customized virtual surface. I was working with this in my other machine (6core i7 /32gb ram), which runs Sonar Platinum as main daw. The procedure to use NYRV Agent is simple, you just let it "scan" at your vst plugin folder and after a while the plugs are available from within the Agent plugin's interface. Agent is a 64bit vst plugin itself, and it can load up to 16 vst fx plugs in one instance. And then it occurred to me, why not use this with Acid Pro, and instead of having JBridge bridge the myriad of fx plugs i have, let Agent scan my vst fx folder and then just use JBridge on NYRV Agent itself. And you know what? Worked like magic and solved a lot of problems i had with just JBridge and Acid Pro. A major problem i faced with JBridge and AP: Late generation Waves plugs (version 9 and forth),when bridged with JBridge, they "lose" their automation ability inside Acid Pro, the automation is greyed out (not available) or there is only one available parameter. I contacted JBridge's author for this but as willing as he was, ultimately he wasn't able to help me with this. But with Agent every vst fx plug works perfectly, plus i have control on multiple plugin parameters gathered neatly in one easy to use workspace, and midi learn on every one of them so i can assign the parameters i want to use on my hardware controller and tweak away in less than a minute.
Well, some limitations still apply. FX plugins that receive midi key input, still have this ability disabled in Acid. Plugins that change pitch and tempo like Melodyne Vst can even crash Acid, like make it disappear lol. But i can live with offline editing in Melodyne, to me it's a small price to pay considering the gain.
Beware i am no affiliate neither work for any of these software companies, i 'm just a guy with a studio who likes Acid Pro more than every other daw