Regarding the memory requirements, I think that 64MB is too small for Windows XP, given that Microsoft already recommends 128MB min to run Wndows XP. OK, XP is now faster with Service Pack 2 which reduces a lo the memory footprint of the Windows Kernel, but this is already a huge gap.

We should probably indicate 128MB min on Windows XP, 256MB is anyway very recommended to run Windows XP, even without Limewire...).

What users should do:
before running Limewire, try optimizing your system, without any running application, so that the commited memory will remain low. On windows XP, you can see the amount of committed memory in the System Monitor (an optional component not installed by default). Look also with the Task Monitor (CTRL+ALT+DEL) which process is taking much of memory or resources.

Beware of spywares/spamwares that often take huge amount of memory, notably if your system is running for long (as they are often badly programmed and constantly leak memory).

Use also some tool to check the programs that run in autostart. Many programs should not run automatically just at startup. For example, you don't need to let the Java Update process run in autostart. But one of the most frequent program that take LOTS of memory, and causes slow boot of Windows is the RealNetworks update and notification monitor. If you have Real Player installed, you can just remove the automatic notifications.
You probably also don't need to run at each boot the OSA.EXE (an "optimizer" for Microsoft Office, that loads lots of DLL and take too much time to boot).

If you're short on memory (with less than 256MB on Windows XP), try disabling the Services that you don't need (for example the Microsoft Personal web server, if you don't need to host web pages on your PC; it is not needed to run FrontPage, if you just edit HTML pages that you will test on a remote webserver).

If you don't have a LAN network (and no network printer with a Ethernet adapter that can be used in the Network neighborhood), you probably also don't need to load the Microsoft Windows Networking components (open the Network properties panel, and remove the support for shared files and printers on Windows network, as well as the Client for Microsoft Windows networks); also you may disable the support for NetBIOS in TCP/IP settings...

Disable also the Microsoft Indexing Service (this just takes huge space on your drive to create, very inefficiently, an index of the files you have on your disks, so that the Start>Search wizard will run "faster".) The indexing service also installs its own web server on your PC, and slows any file creation or modification you do.

You may also remove many notification icons installed by default with some display adapters, or sound cards (to control advanced sound effects): use the Display control panel or the Sound/Mixer instead when you really need to change something in those adapters...

In most cases, LimeWire is slow only because the native system is already slow and unnecessarily filled by tools and services you don't use or need.

Note: in the Services Administration panel, don't disable too many services, note the changes you make there so that you can restore them later if another service can't work without it.

There are some great tools on Windows to tweak your system for speed.

But avoid using the network speed optimizers. They are often not very effective and in fact may break the compatility of your network installation with some Internet services, or with some ISPs (for example, disabling PMTU discovery, or BlackHole discovery may result in dramatically slower accesses to some websites).

Note that some Windows tweaker tools will force you to disable UPnP support. This is a bad idea if you're firewalled or use an external NAT router: without it, you'll need to manually configure LimeWire so that it will accept incoming connections through your firewall, and such manual configuration, left permanent, is also a security issue as it will allow worms possibly running on your PC to work as open-relays that will steal your bandwidth... Using UPnP is *now* (with security updates) often safer than using manual configuration without lots of precautions, notably if you have an external router or external firewall that will protect your local (or builtin in Windows XP SP2) UPnP-enabled firewall.