When I run Recuva it uses essentially all my remaining memory (leaves ~100MB free), but reaches that amount of memory usage early in the scanning process (so it's obviously using the pagefile after - since it continues running fine even after memory usage hits 99%). The problem is that when Windows is (almost) out of RAM, the entire system slows to a crawl (and that's putting it kindly). This means the analysis of the discovered files takes much longer than it should - about 40files/sec for my last run, and when Recuva discovers, oh I don't know... 2,000,000+ files (or, if allowing for securely deleted ones, ~6,000,000 files) that's A LOT of time analyzing
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I got around this by using Firefox and waiting until it used about 130MB of memory before running Recuva. Then, when Recuva was done scanning and started analyzing the files, I killed firefox (freeing its memory): Recuva finished analysis in 3 minutes!
I'm not sure how this would be... fixed (it's not stopping Recuva from working so I didn't list it as a bug, but it's severely degrading its performance) within Recuva itself, but it's something to consider finding a solution to.
My System (in case it helps):
Vista Ultimate SP1
2GB DDR2
Intel Core2Duo 2Ghz
Recuva's a great program, keep up the good work

Cheers,
DEBob