my system is fine in general, its not due to some general misconfiguration of windows.
I have 2 HDDs in my system, 1st one includes the OS (C:) and a logical partition (D:), on which all my downloads are located. my "workdrive" is G:, which is to be my complete 2nd HDD. so the problem is when decoding takes place and then at the same time par2 checking and reparing, then my 1st main disk has to read at the same time from HDD for decoding and for checking/repairing, which is the problem here. if this took place on the other HDD G:, then everything would be fine. but currently the automatic switch over to another dir/drive which can be made by altbinz only takes place at unraring, when the crucial work, which slows down the things most is already over. I also cannot just switch drives for these tasks, as I dont have that much space on my drive D: for downloaded and extracted files at the same time (before they get deleted), the big space is all on that other drive. apart from that, when I changed the download folder to that drive, I'd have the same problem again, then both processes, decoding and par2 checking/repairing would both take place on the same drive again. the aim should be that alt binz could automatically divide those processes up on 2 different drives, if desired.
its basically the same when for example playing a larger file from CDROM and then in explorer you try rightclck -> attributes on another file, then your system will also slow down significantly, because the head/laser has to be at 2 different places at the same time and here in usenet context this is additionally connected to heavy load.
I'll give that ram cache decoding a try though, maybe this might help.
edit: tried this now, gave 300mb of max chache (am downloading 200mb files) and set remove articles to 1 min (the cache should be empty again for each file). I dont know if these numbers are maybe wrong or not that efficient, but I tried unraring a file at the same time from the same disc and the decoding process was 3x faster when I paused unraring (at least you can pause unraring, while this is not possible for par2 work).