Since nobody else has offered any suggestions I'll jump in.  I wonder if the problem isn't somewhere other than Quicken? I have Quicken an old Xp machine with records since 1/1/94 and I can't say it is sluggish.  It's a Dell 2.2 Ghz Pentium 4 I bought in April 2003.

It's my records computer.  It isn't online, I don't play games with it, but it does have LOTS of records.  My business records, 16 years of church board minutes, lots of photographs ... maybe I need to do another backup.  But (staying on topic) it is not sluggish.

My guess (based on my experience ... sometimes an expensive teacher) is you may just need a little maintenance.  Backup important data, delete temp files, uninstall old programs you don't use and never will use again, defrag the hard drive, etc will all help and might solve your problem.  It did for me.