These options and tweaks are all very simple to understand. I'll explain them here, and you can decide whether you want to check them off.

The first tab, General 1/2, looks like this:

An explanation of the options follows.

Classic Setup Look - Use the Windows 2000 setup look, as opposed to the "new-age" Windows XP setup. I prefer the classic setup, as it tells me more about what's going on, and it feels snappier.

Black setup background (only available if you check the above) - Use a black background for the classic setup, as opposed to a wallpapered one.

Disable SFC (File Protection) - Disables System File Protection. This will save a large chunk of disk space, but will open you up for the possibility of DLL Hell, as programs will be able to replace system DLLs with their own. SFC automatically restores modified/deleted system files from its cache when it is enabled. I recommend that for a long-term use system you should leave SFC enabled, but if you want an uber-tweaked out system purely for gaming or some other purpose, you can probably disable SFC.

Unsigned Themes Support (only available in XP) - Patches uxtheme.dll to enable unsigned (custom) Windows themes. You no longer need programs like StyleXP to enable custom themes if you do this.

Merge Driver CABs - I would suppose this merges all driver cabinets into one larger cabinet, but I can't modify this setting, as the checkbox is grayed out.

Remove duplicate files - Removes duplicate files from cabinets which are already in the i386 folder. You should use this only if you will be installing Windows from the CD.

Higher compression of drivers - Uses a higher compression setting for drivers, at the expense of slowing down extraction a bit.

Disable HDD free space requirement - Disables the check for the minimum hard drive space requirement.

Disable minimum memory requirement - Disables the check for the minimum memory requirement.

OEM Branding - Brands the Windows installation as an "nLite'ed" installation as far as I know. I've never used this, so if someone would be so kind as to either confirm or deny this, it'd be appreciated. Update: Thanks to Master of the VG for confirming this and providing a screenshot!

The second tab, General 2/2:

Profiles Path - The path of user profiles. Leaving the default of "%SystemDrive%\Documents and Settings" results in a profiles being stored on the system drive (usually C:) in a "Documents and Settings" sub-folder. If you are going for a totally user-data-independent-of-system setup, you could use something like "D:\Profiles", so that even when you format C: to re-install Windows in the future, you don't lose any of your personal documents. Note that you need to have a formatted partition before Windows Setup begins if you want to use a drive other than %SystemDrive%. This would be particularly useful for those doing Matrix RAID and any other sort of RAID0 setup where you want important files to reside on something a little less volatile.

Maximum unfinished simultaneous connections - This is what is known as the SP2 TCP/IP patch. In SP2, Microsoft limited the number of simultaneous incomplete outbound connection attempts to 10, with the intention of slowing down the propagation of worms. While this limit doesn't affect most users, many people report problems with P2P software, as well as security scanners. Here you have the option of patching Windows' tcpip.sys file to change this limit. I usually use 128 to 512. You can pick anything, though going above 512 is overkill.

Keep keyboard layouts of removed languages - If you need them, check this. If they can be removed, leave it unchecked.

Large Partition Support - If you are using pre-SP1 XP installation sources, you will have this option. It removes the 134 GB partition size limit by enabling 48-bit LBA (Logical Block Addressing). If you have integrated Service Pack 1 or 2, this option will be grayed out, as SP2 already uses 48-bit LBA.

Keep Windows Media Player compatibility - If you have removed Windows Media Player earlier (in the Remove Components panel) because you plan to install the latest Windows Media Player yourself, keep this checked. Unchecking this will prevent you from being able to install any WMP if you've removed it.

Disable nLite.inf - I've actually forgotten what this does, but I remember that checking it is not recommended.

The last tab, Tweaks, contains too many options to name (let alone describe!). Fortunately, the tips provided below the list are quite clear -- just hover your mouse over an option to see its tip. A couple of the very useful ones include "Explorer->Add CMD SHELL:>to all Drives and Folders" which allows users to right click on a folder in explorer to open up a command prompt in that directory and "Explorer->Change Explorer Folder View to: details" instead of the ridiculous default icon view.

Tip: Don't disable the page file, don't disable paging of the kernel and core OS, don't disable the prefetch cache, and don't disable DCOM. Other than that, check off whatever you like. :-)

Click Next when you are done.