Well that obviously doesn't sound right
Even with a low spec machine it shouldn't take anywhere near that long. As an example, my single processor PIII750 inserts a batch of 500 into the database in 2 or 3 minutes. This is with just under a million posts.
There are few things you should check.
1) The Perl version and it's modules. The Perl version should be 5.005_03 or higher and make sure you have the latest modules.
2) Make sure all indexes are in place in the database. Critical indexes are on the msgid columns and the refs columns. Also make sure all the original vB indexes are in place.
At what point is the delay occuring? What is displayed on the screen?