What is critical are the other processes that start on boot and you don't mention any of those. With your limited RAM you have to be brutal with what you allow to start on boot, only absolutely no non-essential applications, security apps only, AV, Firewall and windows services.
Your RAM is really an issue, 256MB with XP really would be considered a minimum and then you add other applications so there will be much swapping RAM content out to the pagefile.sys so lots of HDD thrashing. If your HDD isn't particularly fast that too would be another bottleneck.
If you have an integrated graphics card that too will be grabbing RAM and since you report 248MB of RAM and not 256MB that could be why.
Whilst your system is a little underpowered RAM is your biggest issue. My advice get at least another 256MB to take you to 512MB of RAM, or preferably upgrade to 1GB and you will see a drastic improvement in system response and not just at boot.