Why do I get a delayed, sponsored result at the top of the results?

Question

Using Firefox, when I do a Google search I get a list of returns, and just as I'm about to click on one of the returns, a new one pops up a the top of the list, one that is possibly related only because it has one of the same words submitted in the search, but is typically far afield and appears to be a commercial 'leech' attempting to get to their site.
This delayed entry shifts the whole list of returns downward, and if I happen to be clicking on the first entry of the initial list, I end up clicking on the delayed entry. This is annoying in several ways. It delays my search because I've unintentionally clicked on a return I didn't want. More than that, though, is that the delayed return is an insidious form of commercialism, one that defies that usual 'user friendliness' of Firefox.
What is this delayed return about? I don't see anyone else complaining about it. I don't have this experience in Safari, and I was kinda hoping I wouldn't have it on this new machine. But no such luck.

Answer 1

Do a malware check with some malware scanning programs on the Windows computer.<br />
You need to scan with all programs because each program detects different malware.<br />
Make sure that you update each program to get the latest version of their databases before doing a scan.
*http://www.malwarebytes.org/mbam.php - Malwarebytes' Anti-Malware
*http://www.superantispyware.com/ - SuperAntispyware
*http://www.microsoft.com/security/scanner/en-us/default.aspx - Microsoft Safety Scanner
*http://www.microsoft.com/windows/products/winfamily/defender/default.mspx - Windows Defender: Home Page
*http://www.safer-networking.org/en/index.html - Spybot Search & Destroy
*Kasperky Free Security Scan: http://www.kaspersky.com/security-scan
You can also do a check for a rootkit infection with TDSSKiller.
*http://support.kaspersky.com/viruses/solutions?qid=208280684
See also:
*"Spyware on Windows": http://kb.mozillazine.org/Popups_not_blocked