I have FSX and vista.
I originally installed FSX and i had no issues with virtual momory. Then i installed [Mod - lovely stuff]loads of freeware airplanes to the point FSX took decades to load. I got tired of that and so I tryed deleting freeware aircraft i didnt like.. ended up deleting the handglider which is a FSX default so now FSX took even longer to load due to the fact that it had its main aircraft deleted. So i decided to reinstall FSX but for some reason i forgot to do a clean install. After that i started having virtual memory errors. So I increased the virtual memory size to 9