mIrc backdoor flood

I originally posted this (by mistake) in the dvd ripping section where I promptly had my ass kicked by the mod, sorry mod.
My problem is that I recently had the mIrc back door flood on my computer I managed to delete it and my computer seems to be fine now but in so doing I deleted the following C:system32/softreg/svchost.exe and now , every time I boot up I get a nag box saying C:system32/softreg/svchost.exe cannot be found and then another saying if it is not on the computer to remove the reference to it from registry.
Firstly is C:system32/softreg/svchost.exe a Windows file and if so where can I download it I tried Microsoft download centre to no avail
If it is not needed how can I remove reference to it from the registry. Any help would be much appreciated.