Windows Check Disk always starts on computer boot

I just built a new system, ASUS P5K-E Wifi with Intel Core 2 Duo E7200 2.53Ghz processor and 2Gb Corsair RAM. I have two hard drives, one connected to SATA and the other ATA. I have had these hard drives connected in the same way before on my old motherboard (Asus P4P800S) and had no problems. Everytime I start my computer Windows XP wants to check disk on E: which is my ATA hard drive. There are no errors when after the disk check is completed and both hard drives function properly without any problems. The hard drive that always goes through the check is one of my extra hard drives that I use for backup and storage. Any ideas as to why this would be happening? Thanks!