MacBook – MBP 13′ (mid-2010; 7,1) 2.4 Core 2 Duo P8600 supporting 16 GB RAM under Win7

First, let me explain the problem a little: in 32-bit mode, the processor can only address 4GB of stuff. The problem is that "stuff" doesn't just include RAM, it includes RAM and memory-mapped I/O, most notably the video card. Since your new iMac has a bigger, better video card (with more video memory), it takes up more of the 4GB address space and there's less left for actual RAM.

There are several ways to make more RAM accessible to your program:

• Switch to 64-bit Windows. This allows the OS to address all of your RAM, and is really the right way to solve the problem. If you can't recompile your custom program for 64-bit mode, it should be able to run in 32-bit mode thanks to the WoW64 compatibility layer.

  Downsides: you'll have to do a custom install of the OS (meaning you basically start from scratch). There's also still a possibility that the program won't work (most likely if it includes 32-bit device drivers), and in this case you'd have to do another custom install to get back to 32-bit Windows. So, while this is really the best solution, you might want to try the other options first.

• Enable physical address extension (PAE). If the driver supports it, this'll allow the video memory to be mapped above the usual 4GB limit, allowing you to use more of that 4GB for RAM. I haven't used this, but it looks pretty easy to enable and disable, so I'd be tempted to try this first.

• Enable 4-Gigabyte tuning. This shifts how the address space is allocated, giving applications more and the kernel less. I'm not sure how this'd work (or even if it would work at all) in your situation, but it is another possibility. It can also be used together with PAE, so you can try different combinations to see what works.

If you really want to make your old mac happy I would say the best thing is the SSD. It will make it feel faster than it was out of the box and that is because it is. A RAM upgrade isn't really necessary and I would suggest investing that money over into a new battery. If the unit hasn't been used in a good long while chances are your battery will be dead or inches away from death.

A new battery (directly from Apple) will be guarantied for a year and will give you a notebook to take with you (using an SSD instead of a HDD also gives you a few extra minutes in battery life.

CleanMyMac is not recommended! Instead install a new OS on the SSD and then using an external enclosure transfer the data via Migration Assistant. But always make sure you have a backup of your files.

Honestly I am more of a fan of keeping things fresh and installing 3PP programs fresh too and manually dragging over your documents, pictures, music, etc.