I used to use the old Cakewalk FX 2 Tape Sim effect; I believe it is Direct-X.
It's no longer included in the install of X3; but you can download the .EXE install file for free.
Question: it says that this is for Win 98/ME/XP - but I had this running on a Win7 system at one time. Is there any danger of installing this on my Win7 64-bit system? I assume that this is a 32-bit plug which will use bitbridge etc.?

Direct-X plugins (installed or not) won't reduce your performance unless you actually use them.
I believe it only loads up when required: http://windows.microsoft.com/en-gb/windows-vista/directx-frequently-asked-questions
 
Or are you saying you want to install this? If so it will probably work but don't quote me (personally I wouldn't install it).

BitBridge only works with VST plug-ins. Do not bother with the free downloads, they are 32bit DX versions. The FX 2 Tape Sim, Amp Sim and Pitch Shifter were ported to 64bit and included through X2. If you uninstalled X2, you can re-install the plug-ins using the advanced install option. The rest of the old FX1-3 plug-ins were not ported to 64bit. For all I know, they may be optional components in X3.

Ah - okay - I can re-install with my X2 - thanks!

While you are running the X2 advanced install, you might want to install R-Mix too.

what about the old FXREVERB?

dude24man
what about the old FXREVERB?

32bit DX only. 32bit DX plug-ins may work in 64bit SONAR using a DX-to-VST wrapper and loaded with bridging software.

What I've found in the past is that only 32bit DX plugins in .dll file format can be wrapped.   Unfortunately the FX Reverb, as well as Flange + Chorus I believe, is not, instead being in .ax file format.
 

Yes, it is a mess and for those that really need the older Cakewalk plug-ins (and older plug-ins in general), the best solution is to install the 32bit version of SONAR.