I have lavasoft program Ad-aware. When I use it, the program always detects spyware called Doubleclick. What exactly is this Doubleclick?

aps
Dell Dimension 4100
Windows ME
1000 megahertz Intel Pentium III
BIOS Version 8
128MB 133MHz SDRAM
32MB NVIDIA TNT2 M64 AGP Graphics Card
20 GB ULTRA ATA-100 HARD DRIVE
V.90/56kTelephony Modem
12X DVD Rom
SB Live!
Altec Lansing ACS340-Speakers
100 MB Zip Drive
IE Version 6
Outlook Express Version 6
Zone Alarm Pro
Cable Modem