Maybe check your machine for viruses? I have a CPU and memory in the same ballpark (RAM is exactly the same, actually), and when unzipping the Alexandra archive file, my machine uses maybe 6MB of memory and maybe 2% of the processing power. There's no way your machine should be straining so hard to do something so simple. If it's taking your computer that long, something is seriously wrong, bogging your PC down.
except unpacking Maids and maidens for ex, it did so at around 4.8 Mb/s. It is only the occassional title it bogs down to no end with; and it makes no sense to me at all. I run an always on AV and an active web monitor for virus/malware.