Ten days later you sell all shares in acct #1 for a profit for all 100 shares.  Then 15 days later you sell the other 100 shares in acct #2 for a loss.  My question is:  if you repurchase the same stock (MSFT) in acct #1 within 30 days of the original sale will this result in a "wash sale" to the new purchase in acct #1?  Or will the wash sale only apply if I repurchase within 30 days in acct #2.

the 1st sale at a profit has no effect on wash sale determination.

purchase of replacement shares of a substantially identical security within 30 days of the loss sale in any a/c including a tax-deferred a/c such as an IRA will result in a wash sale. since it seems you had no replacement shares purchased before the loss sale then only the 30 days after would matter (the sale in a/c 2).

note with 2 different brokers you would have to manually adjust for the wash sale since neither would know what you did.