Longer Boot time after upgrading the Hard drive

http://www.mercury-pc.com/downloads_list.php?productid=54

You need 333 bus DDR II RAM 512 MB

Yes, any motherboard that supports "larger-than-32GB" disk-drives should support larger disk-drives.

Yes, most motherboards support up to 512MB per stick of RAM.

Have you tried resetting the CMOS? Often, after upgrading BIOS you need to clear the CMOS and re-setup to handle the new features. You should have a jumper to clear CMOS, or you can remove the power from the system and remove the battery for a few seconds to clear it.

Let me know if this clears up your issue.

Upgrading the computer to the faster CPU, memory, hard disk, can be possible. First find out the motherboard supports higher CPU already , then find the right CPU for the upgrade,. Maximum memory that can be added in the comuter and type of memory supported by the motherboard. If you need more capacity for Hard disk get high capacity harddisk that the computer support. More important is make sure that the upgrade doesn't require to buy new operating system. Most upgrades are not cheper than purchasing new system considering all above needs. If you require to upgrade to more and latest system than it is better to buy a new system including operating system. The operating system may not support considerable difference in the computer system for upgrades.

Looking at the manual for this motherboard your maximum ram is 512mb in two sticks of 256mb each. Speed rating is pc133 (maximum). You may struggle with the external hard drive as you only seem to have usb 1.1 and not usb 2.0

The best place to download drivers is always the manufacturer's website. The XP drivers for this system are found here :)

http://www.mercury-pc.com/downloads_list.php?productid=53

I want disk driver for Motherboard P4M266

this may help you http://www.mercury-pc.com/downloads_list.php

your cpu does not have much to do with the hdd you may be getting...
technically you should have no problem by getting the largest hdd you can afford. what you may want to take into consideration besides your budget is:
what os you're using.. dos, win9x, xp, vista?
a. if you have dos the smaller you can get probably the better as you may not be able to create a large partition. (chances are you may not get anything new smaller than 40 gigs.. and that would be a big waste of money and hard drive room)
b. if you have win9x, your probably using fat32 for your filesystem meaning you may not be able to go above 32 gig when creating your partition and formating your drive.
c. if your using win xp or vista... and your planning on using NTFS when partitioning the drive instead of FAT32...(as you should unless your operating system is on a FAT32 partition) you can go for the largest hdd you can afford.