Well if you have reinatalled the operating system it does cut down what would have been a very long list to check.

Slow loading from disc could be caused by: -

1. Anti-Virus Internet Security products like Norton that have an active checking of opening software mode enabled.

2. Hard Drive running in PIO Mode rather than Ultra DMA - check the settings in Device Manager -> IDE ATA/ATAPI Controllers -> Primary IDE Channel -> Advanced Settings

3. Badly Fragmented Hard Disc or Many Bad Sectors.  Run CHKDSK and DEFRAG.

4. Windows Indexing Services

Just a few ideas for you to check - perhaps others may have some more suggestions.

Have you tried it after a System Recovery and before you add any software?

Also 'Perceptions' of what is slow can change over time!!!