Resources have nothing to do with how much RAM you have installed.
Win98 will use as much unused RAM as possible for caching information which really speeds things up. Open a program you havent opened since you booted that takes some time to open. Close the program and reopen it any time before you reboot and it will open three times as fast because it is taking code from the cache in RAM. Windows 98 and above will give the RAM up from cache instantly if it is needed by programs. Win95 did not always give the RAM up and they came up with those Turbo/Mem/Free/Max/RAM type programs to apply an artificial demand to flush the cache. You dont want to flush the cache in Win 98/ME. Get rid of the programs as they do only bad things if you arent running Win95. With 512Mb RAM there is absolutely no reason to be messing with Windows RAM management.
You can check your RAM with this:
http://www.zdnet.com/downloads/stories/info/0,10615,56531,00.html
What indications are you getting that your computer is using up all of your RAM? Using Photoshop with large image files is RAM intensive. Editing streaming video can be RAM intensive. Installing programs and running virus scans is NOT Ram intensive people with 64Mb RAM do that just fine.
You have to sort out what is causing the lockups. I recommend TclockEX. It is a freeware clock that replaces your system clock and provides good information.
http://users.iafrica.com/d/da/dalen/tclockex.htm
The yellow bar across the top of the clock indicates CPU use. It should be at just about zero except when the computer has just been told to do something or is performing a specific task you know is CPU intensive.
The green bar across the bottom is the used RAM. Optimum for most people is to have all of the RAM used all of the time since it is fast, but it is hard to do with 512 Mb RAM. I leave my computer on 24/7 so I dont flush my cache and have never cached much over 300 Mb. You will notice his RAM bar extends almost all the way across leaving no or little available RAM that is the way it should be for someone with 128Mb RAM and even for someone with 256 whose computer has been used for a while.
I think the more significant thing for you is that you can have it display a two digit readout of your user resources to the left of the clock. I dumped the year and seconds so it wouldnt take so much space. Right now mine reads: 75 Sat 24 Nov 1:55: The 75 means I have 75% user resources available. The clock format to do this is: U ddd d MMM h:mm: You can configure it any way you want. I have the colon after the minutes to keep the last digit off the edge BTW.
Your most likely problem is resources. If your available resources just after you boot and before you do anything are much below about 85% you need to clean out the programs that load at boot. Get back with your resources immediately after you reboot, and what they are reading just before you get lockups.