With 512mb of RAM you won't be able to crunch any of these session 192 units, trust me on that. It even failed on my 2nd machine that's got 1GB in it giving the tail-tale out of memory BOINC error code (0x2F)

At 15hrs+ a WU they can be truely evil, espically since they don't have checkpoints so it'll keep crunching those WU's without swapping projects.