Your hdd must be formatted as FAT 32 which has the size limit .
In xp you can easily change the formatting of your hard drive to NTFS . This shouldnt affect your files , but you cannot go back to FAT32 [ but then you shouldnt want either ]
To convert a volume to NTFS from the command prompt
Open Command Prompt. Click Start, point to All Programs, point to Accessories, and then click Command Prompt.
In the command prompt window, type: convert [drive_letter]: /fs:ntfs
For example, typing convert D: /fs:ntfs would format drive D: with the ntfs format. You can convert FAT or FAT32 volumes to NTFS with this command.
Important Once you convert a drive or partition to NTFS, you cannot simply convert it back to FAT or FAT32. You will need to reformat the drive or partition which will erase all data, including programs and personal files, on the partition.