No Idea how to change RAM

I've seen other posts about changing the RAM assigned to the Java process needed to run Bukkit servers, but for some reason, none of them seem to work with my current run.bat. I've tried simply removing my server, and changing my .bat to include 2048 as the max and min, but that doesn't seem to work.
Maybe I'm just using the wrong code? My current run.bat is

Maybe I'm just a complete idiot?

Edit: Also, I'm only trying to increase the ram because I get massive lag spikes after a few minutes, and now I get the "Can't keep up!" after a few seconds of the server being up.

 

The can't keep up message is not always about RAM. As far as i know the CPU can be the problem, or the internet connection (i'm not sure about this last one). Anyway, if you want to increase the RAM. you have to write this:

Anothe thing, a server can run with no lagspikes with 1GB with 3 o 4 plugins. If the cant keep up message appears even without plugins, i will recommend you to get an host.

Sorry for bad english

 

If julikihd 's idea doesn't work, it's probably because you can't allocate more than 1GB(or 2, can't remember) RAM with 32bit java, if this is the case then do as follows;
go to C:\Program Files (x86)\Java\jre7\bin
run javacpl.exe
now a window should pop up looking like this

Now, click on the java tab, then click on "view..."
A window should pop up with 2 JREs in it, disable the the one located in "Program files (x86)"

Only one JRE? (open) Only one JRE? (close)

32 bit and 64 bit java are installed seperatly, if you have a 32 bit computer then I'm afraid you can't allocate more RAM.

go here for 64 bit java

Once you've done that, change the numbers
in your RUN.bat freely.

example 4gb allocation

Code:

java -Xmx4g -jar craftbukkit-1.7.2-R0.3.jar -o true
PAUSE

 

julikihd Thanks, I might look into getting a host after I get all my plug-ins settled
caelum19 That worked, thanks! Lag/Timeout free!

 

Happy I could help.
also, the 4g allocation example was broken, I fixed it now.