Hi,
I have fedora 3 running on P4 2.4Ghz, 512 Mb RAM with a Geforce MX 4000 128MB. I think my comp is a little bit slow to run Wine so I want to buy an addtional 1GB RAM to make it faster. However, I wonder if i do so, I have to reinstall my Linux? I know that the swap partition is decided at installation time and based on my current RAM size, so it I change the size of RAM now, the system will not stable anymore!
Please give me a suggestion.

You don't have to reinstall linux coz it should be autodetected. The only thing is, you need to make sure that large memory support is enabled in your kernel or else it may not recognise the extra memory. I don't know whether Fedora enables this by default coz I know other distros do.

How do I check if large memory support is enable on my fedora? If the ram size is automatically detected by the OS, does the swap file also automatically scale up too? Is it true that the more RAM i have, the faster my comp is in linux?
Thank for helping

I usually use the "free" command to check how much ram I have and how much is being used. Also if you have more than 512 megs of ram, you don't really need a large swap partition so the one you have should be ok.

Maybe you even do not need to upgrade? I think such machine would be more than enough to play Unreal 2, because i played hitman 2 with comp half the power of yours.
If you want to speed up, AND save your money, then turn off some daemons. Fedora launches many (sometimes unused) daemons at default, maybe you should use lighter window manager (assuming you are using KDE or GNOME here) like fluxbox or fvwm ( I can mail you my fvwm config, looks really cool, much better than KDE IMO). If you want DE, then use xfce. This would speed up your computer A LOT, fvwm uses no more than 10 megabytes of memory, as gnome uses about 50 or more ( but that is just for me, and my config ).

Links:
fvwm - http://www.fvwm.org/
fluxbox - http://fluxbox.sourceforge.net/
xfce - http://www.xfce.org/

PS.:
And yes, you should not need to reinstall when you add more ram.

EDIT:
Programs like microsoft office 2000 in wine runs even on celeron 333, 256 ram oldie. So if you do not want games there is no need to upgrade.

Thanks a lot for suggestion, I will try to shut somr dasmons down to save some memory. Is there any website that i can use as reference for fedora daemons since i may not know all the fuction of the daemons so i may shut down the wrong one

Just search for the name of daemon here.
You will get more info than you need. If you have questions - ask here.