i will have a look, i don't really want to move the cooler round as it will disturb the thermal paste etc won't it? sorry this is all new to me.
It came pre assembled, i would have assumed they would mount the fan to suit airflow?
As
@Daz... says - if it came like that, it's likely to be the wrong way around. It's not going to ruin anything as such, but it's far from optimal if left like it is.
Moving the heat-sink off is a very straight-forward process - but I wouldn't do it without having some decent replacement paste on the sidelines. Removing old paste is easy with with likes of rubbing alcohol and tissue wipe and again as
@Daz... says - it does make you think how the original paste was applied if the unit is 180 degrees around?
Usually, you can see a little direction marker on the outer edge of fan units which indicate the way the air blows. Just make you have the motherboard on something slightly compliant with some give and free of static - a sheet of cardboard is usually ideal to work off.
Thermal paste loses its efficiency over the years - ending up brittle and chalky. I've been lazy with mine and only swapped it the other weekend after a good 4 years of my system being built. I'd normally aim for at least half that.