What is the brand and model of computer or motherboard? What is the age of the hard drive? What memory is installed? And what are you using for antivirus and antispyware.
The CMOS battery is not known as a cause for a slowdown.
One problem going around now is with Internet Explorer 8... You might try removing that and seeing if it is still slow in Internet Explorer 6.1
But the usual suspects are bad hard drive, bad or inadequate memory, and bad infestations of spyware. The first thing I would do is download and run Avast, or perhaps Avira Antivir and run their full scan. Then use Spyware Doctor full version or SpySweepere, or SuperAntiSpyware and Malware bytes, and see what they find... remove all, and get back to us.