There is no single right answer to the question of what Linux distro is the best or easiest to use. It will partly depend on the hardware, partly what applications you want to use, and also your own experience and expectations.
What I suggest is that you download and install VirtualBox and then install a few different distros to try before you decide.
Here are some of the distros that I've tried and thought were good, though there are many other good distros.
Ubuntu, Fedora, Debian, Slackware, Linux Mint
I use Slackware Linux but it does take more preparation and information to install than Ubuntu, especially the first time.
Before you dual boot with Windows XP there are some things you should think about.
How do you plan to re-partition your hard disk? Some installers such as the one with Ubuntu can automatically re-size your NTFS partition. Slackware and other distros may require typing in commands or using additional software. Back up your important files before you install a Linux distro, especially if you will have to re-size the Windows XP NTFS partition.
You can dual boot in a number of different ways. The default installation of most Linux distros will make the Linux boot loader start first. That means if something goes wrong, Windows XP might not boot and you might have to repair the Master Boot Record using a Windows XP Setup CD. You can choose other ways to install the Linux boot loader but it might not always be obvious how to do that. I usually install the Linux boot loader to the Linux root partition instead of the Master Boot Record (MBR).
What kind of system restore or installation discs did you use for Windows XP? If your computer does not have a normal Microsoft Windows XP Setup CD it may be difficult or impossible to repair problems. You may have to completely reinstall Windows XP and even reformat the entire hard disk. You can boot a Microsoft Windows XP Setup CD to repair problems, but that isn't possible with most computer manufacturers' restore discs. If you're going to dual boot it can be helpful to get a copy of a real Microsoft Windows XP Setup CD just so that you can boot it and repair problems.
If your computer has a hidden factory restore partition (HP for example) then you may have to do special things to install a Linux distro or to keep that hidden partition functional. Take a look at your current partition layout carefully before you install a Linux distro.
It is possible to have the Windows XP Boot menu start first, and then start the Linux boot loader. That's what I do on my system. It requires additional steps after installing Linux. I have to copy the Linux root partition's boot sector into a file, and then copy the file to the Windows XP NTFS partition. Then I have to edit the BOOT.INI file to include Linux as a menu entry. You can use the Linux "dd" command to copy the boot sector or you can download the free Windows XP Support tools from Microsoft and use the "DSKPROBE" utility. It sounds more complicated than it is.
Do you have a RAID configuration? Most PC RAID controllers are "fake hardware RAID". They require special drivers for any OS including Linux. Depending on the RAID controller and Linux distro the installation can be simple or very complicated on a RAID configuration. If possible I recommend installing Linux on a single, non-RAID disk to start with. If you do plan to install on RAID, make sure that the distro is compatible and you know any special steps for installing it on fake hardware RAID.
Even if you expect everything to work great, be prepared with the boot discs and other things that you need in case there's a problem. Back up your important files first, and have another computer that you can use to download files or look for information online.
Do you want Windows to be able to "see" your Linux files? There is a driver for Windows called "ext2ifs" but it is only compatible if you format your Linux file system in a compatible way (using 128-byte inodes). That may require manually formatting the Linux partition rather than using the default installation.
Do you want Windows backup software that can back up your Linux partition? Paragon Hard Disk Backup is one example of software that works with Linux partitions. You have to buy a Linux version to run the program under Linux but you can use the Windows version to back up and restore Linux partitions. You also may need to format your Linux partition with 128-byte inodes for some backup software and features to work.
If you want my opinion about Linux distros, I recommend Ubuntu for a GNOME desktop or Slackware for a KDE desktop. KDE looks more like Windows, and GNOME is simpler but has more graphical desktop effects. KDE is rapidly catching up to GNOME with the eye candy. I prefer Slackware and KDE but I can't argue with anyone choosing GNOME on another distro such as Ubuntu.
If you have a friend or someone who can help you install and configure your system in person, then it might be a good idea to use the same distro they have. If not, take a look at the different distros and install them in VirtualBox. Then you'll know what's required to install them and find out about any problems without affecting your Windows XP system. After you feel comfortable with a distro, then install it to a partition on your hard disk as a second OS that you can boot.
There are some distros designed for special situations or to be simpler to install and use. I'll mention a few of them.
- Puppy Linux - Great for a boot CD or with limited RAM or CPU speed
- Damn Small Linux (DSL) - Good with limited RAM or CPU speed
- Linux Mint - Very easy to install and use (similar to Ubuntu)
Boot CDs that may be handy.
- Hiren's BootCD
- MemTest86.com free memory test boot CD
- Microsoft Windows XP Setup CD (that can run Recovery Console)
- Puppy Linux boot CD
- Super Grub Disk
- Restore discs for your computer model
- Partition backup software boot CD (Paragon, Ghost, etc.)