Slow boot for back up machine

I have a Abit BH6 with a Pentium 3 700mhz and 768mb of ram runnig Xp Pro. I don't use it too much. Run it about 3-4 days a month to update the antivirus and software. Did a clean install last year on the machine. After SP2 boots slower than before. I had SP2 on it before I redid it.The screen is black for about 20-30 sec. before windows starts to load up. I don't think its a virus or spyware scan for both when I run it. Sp2 was the first thing I put on the machine. Is there a way to speed up the boot time?