Accessing a hard-drive partition

A couple of years ago I installed Linux onto my computer. I partitioned my hard-drive into two, since I also wanted to keep my Windows 98 system so I could play games. When I installed Linux onto my computer it also installed some software to let you decide whether you want to boot into windows or you want to boot into Linux whenever the computer boots.

This worked fine while I had Windows 98 on my computer, but recently I decided to upgrade to Windows XP. After I installed XP onto my computer, it seems like that software that allowed me to decide which operating system I wanted to boot up in has just dissapeared, although my guess is that when I installed XP it changed my boot sequence so it just bypasses the software.

My question is how do I get the option to boot between the two partitions back? Is there some way I could just get the old software back or do I need to download something new, or is there something already built in to the computer that I could use.

Thanks for any help.