I do not know how the resource load might differ between PrE 3 & 7, but this ARTICLE might give you some tips on getting the most out of your computer, regardless of version number. I use these tips for any NLE editing session, and I am using PrPro, so the tips are not version, or even program specific.
Hope that this helps,
With "resources," one needs to also consider that there are basically two types:
1.) physical RAM installed, how the OS accesses that and how the program accesses that
2.) Windows Virtual Memory (Page File), how the OS manages that, where it's located and what else is accessing it.
That is where the previous article comes in - those tips will eliminate unnecessary programs and Processes, from accessing either, sapping your NLE of necessary "resources."
For NLE work, I choose to have my Page File set as static (not dynamically managed by the OS), set to ~ 2.5x my installed RAM (4GB on a 32-bit OS) and located where I get the greatest speed. On my workstation, I have it split over my C:\ & E:\ drives. On my laptop, it's split over my C:\ & D:\ drives. It took a lot of testing and benchmarking to establish these locations. Most find that locating it on a C:\, with only the OS and programs, will give more than adequate results. What too often happens is that people will partition a single physical HDD, or only have a single physical HDD, and everything is trying to access that single physical HDD at once, hence a major bottleneck, with slowdowns and even crashes.
I recommend that an editing computer have a minimum of 3 physical (not partitions of any sort) HDD's, and that they are allocated thusly:
C:\ OS, programs and maybe Page File
D:\ media only
E:\ Project files, Scratch Disks, etc.
Note: one could easily swap D:\ for E:\ in their role. That is just how I have things set up on my computers.
And don't forget to resize those photos to no larger than 1000x750 pixels, per the FAQs to the right of this forum. Oversized photos are the main reasons this program shows out of memory messages.
You should also render regularly (by pressing the Enter key) so that any red lines along the top of your timeline turn green.