IE8 swiped my default browser status last night. How do you suppose?

I didn't choose to open IE8 last night. I rarely do. I first noticed it opening with an Ashampoo giveaway when I clicked to get the full version key. I thought the problem would just be limited to Ashampoo, but then my e-mails started bringing up IE. I just checked my default browser, and it had in fact lost its status.

I changed it back, and now the Ashampoo giveaway opened in my default browser.

For me when IE8 comes up it usually just spins without landing on a page.

Windows XP
Home Edition
Version 2002
32-bit
Service Pack 3

Dell DIMENSION DIM2400
Intel(R)
Pentium(R) 4 CPU 2.66GHz
x86 Family 15 Model 2 Stepping 9
2.05 GB of RAM
Graphics Card: Intel(R) 82845G/GL/GE/PE/GV
Graphics Controller, 64 Mb
Hard Drive Size 114.4GB
Free Space was 35.8GB; now under 20GB because after backing up My Documents on Google Drive, Google Drive has duplicated the whole darn thing on my hard drive
Motherboard: Dell Computer Corp., 0G1548
Antivirus : Webroot Internet Security