I am trying to determine fill factor for my indexes. To do that I think the best idea is to use windows performance moniter to moniter the amount of reads and amount of writes. I have set up 2 counters:

For Starters.. What is your current Index Fillfactor? What type of DB is this..Percentage of Read vs Writes ? Index FillFactor is directly proportional to Read and inv prop to Writes..So what this means if Fill factor is close to 100 % it means it is optimzed for Read, but it affects your write because any Insert you do will create page splits..So there is no magic bullet there..it all depends what you are trying to do...

Counters you mentioned measures Disk I/0 that is not exclusively for DB Disk I/0 so there must be something else that is causing writes/sec counter to spike,it may be nothing to do with your DB Disk I/O.In Windows Server 2008 there are ways in Task Manger to figure out what exactly is writing to Disk but don't remember in Windows 2000...

Index fill factor is defaulted to 0 (same as 100%) I understand if i reduce it too low its gonna effect my reads. But my tables are being updated a lot so there is no point of having fill factor of 100% which is only stuitable for read only table. I was thinking something like 90%. But I need to look at performance moniter data to make sure.