well, I am running 32 bit Vista premium edition.
Hmmm... you don't give a lot of detail on your own system but let imagine that your brother ( with SLI GTX 260, 8 gigs of ram and quad core ) use 32 bit Vista prenium edition...
32 bit windows system allow only 4 gb address range for ram ( unless your use a PAE kernel )... from these 4gb, some ram is removed for material... if like me, you have a 8800 ultra 768 mb, you will loose already 768 mb address range for only the graphic card... netwerk card/ship, sound card/ship, ide interfeca, etc use some ram too...
Now, let imagine the perfect situation... you use the PAE kernel who allow 36 bits address range... address of your material will be placed over the 4 gb limit so you will be able to enjoy the full 4 gb for your system...
From these 4 gb, 2 gb is reserved for application and 2 gb for the kernel... unless your use the 3gb flag ... who allow 3gb for application and 1 gb kernel ( who is a ninimum for vista )...
PAE and 3GB are easy to implement in Win XP from service pack 2... only need to modify your boot.ini... Vista is more complex and you need to manipulate register key...
Using 64 bits vista will help you a little... a 32 bits apllication like sins run in the WOW64 mode on 64 bits system... this allow 4 gb by application...
So, at the maximum, with Vista 32 bit, you will have 2 gb for application... don't forget that these 2 gb will be shared with the game, the anti-virus, the firewal and any other application running...
Now, some memory use for sins... i have no result with sins alone but i have result for sins with the mod 7DS 2.0 who will be out in a few days... OS used was linux since in one case, Windows have not allow to start a game due to the lack of enough memory address range ( mini-dump )
All graphics option on, resolution 1680*1050, AAx4... Huge Multistar map with one human player, 9 AI and 1 pirate... these value are start value, they grow with time
gfx on low : 1.0943 gb
gfx on medium : 1.2324 gb
gfx on high : 1.5051 gb ( in 32 bit system, game start but in a short time, mini-dump appear due to shortage of memory )
gfx on very high : 2.2962 gb ( don't work on windows XP 32 bits or Vista 32 bits because over the 2 gb limit for application )
Have just finish two more test... same configuration but with mod dissable...
gfx on low : 0.5943 gb
gfx on very high : 1.3901 gb
So in 32 bits sytem, any configuration will start a game... but in very high, the game is only 0.61 gb before the 2 gb limit... soon of later, with huge fleet, with planet fully developed, with numerous commerce ship... you will reach the limit...
Now about Vista... if you have a legal version, you have receive two package... a 32 bits version and a 64 bits version... if you have 4 gb or more, install the 64 bits version... same if the game is not a 64 bits application, it double the ram that a application can use for run... from 2 gb to a max of 4 gb...
Before you reply me that other high quality game like crysis, mass effect, etc run without problem, you need to understand the different between sins and other game... a lot of other game load a first map, followed by a second once the first is finish, etc... Sins need to load everything at the start because the "galaxy" is created at the start... Now, imagine all these top game loading all the maps in the same time... the memory use and lag will be more bad that with sins...
All this post was valid if your computer using Vista 32 bits was with a similar configuration that your brother computer... if you have a other configuration, maybe other "tuning" will allow some ease for the game...but i need the informations...
About Vista... Microsoft have release a KB ( update ) some time ago who resolve some problem in some game ( sins was one of them )... be sure that your system is fully upgraded... It was not a Stardock issue but a Microsoft one... Same think with the Nvidia card... when sins was released, there was a lot of problem with Nvidia card... problem was with the nvidia driver... it was corrected a few month later by a new nvidia driver... if your computer is one year old, that you have only install the driver from the CD, a lot of change that driver will lead to some problem...
For any game type of game, a 2.66 ghz processor ( better two core ) will be more that perfect... a top graphic card is not needed... RAM use was always a issue with sins... but the very recent sins update include a lot of memory optimization...
Myself, i have be working on optimization too... have make some test who was successful... have calculate that for a game with very high GFX setting, 350 mb of ram can be reclaim from the sins 1.05 ... if i have time, i will maybe release a mini mod later for low end machine... just need to modify all .mesh file, modify all da texture and delete the nm texture... i simply use the specular effect from the da map, specially the blue channel for create the bump map effect... since the nm map in sins is not a real normal map but a bump map, i can delete it... a sample of the result can be see below... the ship have a lot of relief, almost all made using the blue channel of the da map... and be sure that i am not a guy who know better that Stardock... at the begin, it is a error manipulation of my texture who have lead me to these solution...
Danman, the upper God of the mod 7DS have already find several way for go over the limit of the game... the Babylon5 mod have made ship with moving part ( thing who was say to be impossible when the game have go out last year )... Stardock itself have make some miracle in the last update related to speed and memory use...
Enough blah-blah... please, post a detail of your material, OS, sins version, etc... i don't promise that i will find the miracle solution for you but i will try... it don't work, you loose nothing... it work and you become happy...
EDIT : forgot to post the picture of the ship with nm map but using the da map for the same effect... all the dots at the top, the big round thing on side with a light iside, the motor like thing at the extemity of wing, and more are created with the da map, no nm map was used...
PS: this model was made for the Halo mod of canadaman... a little publicity for him